While TV and movie rentals and purchases have been available to Windows users for about a decade now--I last checked out this scene two years ago, if you're curious--two recent developments in this market have made it suddenly much more attractive to users. First, Amazon announced its Unbox service, providing movie purchases and rentals, and TV show purchases, via a truly usable Web-based interface that is decidedly Windows friendly. Much more recently, Apple dramatically expanded its iTunes Store to support movie rentals for the first time--it had previously offered both movie and TV show purchases only--while offering crucial new living room support via an improved Apple TV set-top box. Suddenly, finding commercial video content is much easier. The question is, which one is right for you?

There are various ways to evaluate today's TV show and movie services. But I think the market is neatly and logically bifurcated between Apple's offerings and the others, which all tend to use Microsoft's digital rights management (DRM) scheme. If you're looking at this from a high level, then, the decision about which service to use might be dictated by whether you're in the iTunes/iPod/iPhone camp. If you are, Apple's service is the overwhelmingly obvious choice. If you're not--that is, you use a mix of Windows PCs, non-iPod portable device, and perhaps a Microsoft-friendly living room solution like an Xbox 360, a Media Center Extender, or a Windows-oriented digital media receiver--you should consider the other options.

The nice thing is, all of these solutions work fine on Windows. There's no reason you can't mix and match as your needs require. If your preferred service doesn't have a TV show or movie you're looking for, just move down the list.

Amazon Unbox

I've really grown to like Amazon Unbox, despite my less-than-stellar experiences in years past with other Web-based solutions like CinemaNow and MovieLink. Yes, you have to download a small application to your PC in order to download movies, but it's a simple process, and Amazon offers a unique feature that lets you trigger a download from the Web and choose to have it delivered to another PC. So you could be at work, rent a movie for that evening, and have it download to your home PC so it's ready to go when you arrive there in the evening. Brilliant.

Amazon's Web interface is surprisingly nice, as well, and it works equally well in both IE and Firefox. The selection is vast and includes both movies (to rent or purchase). You can view movies on the PC, a Windows Media-compatible portable device, via an Xbox 360 or other digital media receiver, or even on a TiVo, thanks to the "Amazon Unbox on TiVo" service.

Amazon offers another amazing feature that's unique among these services: Any digital content you purchase from the company (MP3 songs, Kindle books, software, movies, whatever) is stored on Amazon's servers and can be downloaded again and again. So if you rent a movie but forget to download it to your laptop, you can do so later while out on the road. This is a big deal and something that really differentiates Amazon from the other services.

If Unbox has a problem, it's that you cannot browse the service from your living room, unless you have a TiVo: The service is currently available on the Web, and not via Media Center/Extender, so you will need to sit down in front of your PC in order to browse, rent, or purchase content. Once you do that, however, it's a simple matter to view that content from the living room if you have an Xbox 360 or compatible Media Center Extender or other digital media receiver.

Apple iTunes

Apple's service has offered TV show and movie sales for a while now, but the company added movie rentals about a week ago and will add support for these rentals to its Apple TV device sometime in the coming days. As you might expect from a company like Apple, the design is elegant, logical, and about as friendly as they come. Everything occurs through Apple's excellent iTunes software, still my preferred choice for managing music and video content.

One oddity of iTunes movie rentals is that you can basically only have one copy of a rented movie floating around: If you transfer the movie to an iPod or iPhone, for example, you're actually moving the file to the device, not making a copy. Likewise, if you want to then play it back on the PC later, you will have to move it back. I assume it will work the same way with the Apple TV, but Apple has yet to update the device to support rentals, so we'll need to wait and see how that works exactly. On the PC, Apple does a great job of keeping you aware of the limitations of any rental, and when the viewing time will expire.

In my testing (see below), iTunes delivered the best picture quality of these services. Frankly, I'm not surprised, given Apple's use of H.264. I'm looking forward to testing HD video from iTunes too, but that too will require the awaited Apple TV update.

Problems with iTunes are few, but you should be aware of one potentially serious issue: In a bid to drive sales of its latest iPods, Apple has artificially limited support for iTunes movie rentals to the 2007-era iPod nano, classic, and touch, and to the iPhone: Users of earlier iPods need not apply. Also, despite heavily advertising the availability of HD quality rentals, there are no such rentals available on iTunes, at least when accessed via your PC: Apparently, HD rentals will only be made available via the Apple TV, once the version 2.0 software update ships. If I had to guess why this is the case, it would be because Apple's QuickTime software is notoriously performance challenged, and most PC users would have horrible experiences trying to play back HD content.

CinemaNow

Founded way back in 1999, CinemaNow is a pioneer in PC-based movie services. One unique feature: Some of the service's purchased movies can be legally burned to DVD movie discs, a feature that's unavailable on Apple and Amazon. CinemaNow also offers a subscription service: For $29.95 a month or $99.95 a year, you gain access to 1500 "member-only" movies. This includes unlimited access to an adult Web site, which I assume is the real reason for this offering.

What makes CinemaNow somewhat undesirable is the selection: CinemaNow is like the Skinemax of online movie services, though it obviously offers plenty of "legit" movie and TV content as well. There's even a decent selection of "HD" content that's encoded at 8000 Kbps but doesn't appear to actually hit the 1280 x 720 minimum required to warrant that tag.

Also note that you really need to be using IE 6 or higher to access CinemaNow from the Web. A terrible Media Center version of the service is also available.

MovieLink

Recently purchased by Blockbuster, MovieLink remains the traditional digital movie rental and purchase service it's been since its inception. (That may change for some, with Blockbuster expected to open up MovieLink to its Blockbuster Total Access DVD rental service in the future.) As with CinemaNow, I first used MovieLink about a decade ago, and while the service has absolutely improved over the years, it remains kind of an old-school relic in desperate need of a makeover. It's sort of like CinemaNow, just not quite as slimy.

Like CinemaNow, MovieLink requires IE, though you can also access the service through Windows Media Player and Media Center, which is pretty convenient. MovieLink's Media Center interface is marginally better than CinemaNow's, but it's still lackluster. At least it exists, and it works fine from the Xbox 360's Media Center Extender interface.

A note about the testing

Over the years, I've purchased and rented a number of movies and TV shows from all of these services, so I'm pretty familiar with the process. For this review, specifically, however, I thought it made sense to rent the exact same movie from each service so I could make a true apples-to-apples comparison. A word of warning, however: One movie download does not a service make. I know from experience that each service offers a variety of content and that that content can vary wildly, from a quality perspective.

Choosing the movie was, in many ways, the biggest obstacle. I wanted a film I was familiar with and, after discarding "The Simpsons Movie" and "300" as potential choices because of their animated nature, I settled on "Ocean's 13," the latest Brad Pitt/George Clooney casino caper. It's not a great movie per se, but it's perfect for this test because it features indoor and outdoor scenes, close-ups, a bit of action, and, best of all, it's available at all four services.

I was surprised by the head-to-head comparison in some ways. With the exception of the Apple software, which uses iTunes for movie playback, I'm not a big fan of the custom applications the services created for downloading and viewing movies. (Fortunately, movies from Amazon, CinemaNow, and MovieLink play fine in Windows Media Player and Media Center as well.) The quality was pretty consistent, but Apple's version of this particular movie was clearly the best of the bunch. It came in the highest resolution (853 x 356) and had the crispest and sharpest picture, with the best contrast.

(My experience with iTunes movies purchases, by the way, is that they typically arrive in some 640 x [whatever] resolution, so it's unclear whether Apple is bumping up the resolution on rentals. If they are, great, but I'd like to see purchases look this good too.)

The CinemaNow and MovieLink versions of the film appeared to be identical: Both were 720 x 306 and were identical in size on disk. The quality was excellent, but a bit below that of the iTunes version, with slightly less detail. The Amazon version was the lowest resolution--640 x 272--but didn't suffer as a result: The picture looked fine, even blown up full screen on my PC. Also, Amazon's player doesn't actually let you shrink it enough to play back at 100 percent, so it appeared artificially larger than the other movies when played normally. The player also has easily accessible brightness and color sliders which let you readily enhance the picture quality during playback.

Other options

Renting TV shows and movies on a PC is a nice option, but the reality is that most people already have an On Demand service from their cable, satellite, or fiber optic TV supplier. (We use Verizon FIOS for this purpose, and the quality, at least, is excellent.) I think of PC-based TV show and movie services as being supplemental to whatever TV service you're currently using, and even to the local video rental chain. For example, while you may record your favorite TV shows via Media Center, TiVo, or your cable company's built-in DVR, sometimes a glitch happens. It's nice to be able to turn to a service like Amazon Unbox or Apple iTunes in such a case: Purchasing a TV episode for $1.99 is a lot better than missing it all together. I wouldn't subscribe to a season this way, however, as the cost is ludicrous.

PC-based rentals and purchases are more convenient than driving out to Best Buy or Blockbuster, as well, though not as convenient as On Demand. If you can perform these tasks through an Xbox 360, Apple TV, or other living room-based device, all the better: But they're still not as seamless and convenient as your cable box. And of course you have to actually purchase and set up these additional devices too. The complexity of doing so makes them a non-starter for many people.

Also, various companies, including Netflix and Blockbuster, offer DVD rental services. These work well in my experience, though we happen to prefer Blockbuster because you get a free rental every time you return a shipped DVD to the local store instead of mailing it back. Also, Blockbuster emails an astonishing number of coupons out each month; it's a great service. Netflix has a PC-based service that could be of interest, however, especially for frequent travelers who have broadband connections at their destinations: This service lets you view streaming movies while online. (Blockbuster's purchase of MovieLink should even that score soon.)

While people seem to love buying DVD movies, this is an expensive option for all but the most diehard movie lovers. I mean, with a few exceptions, how many times do you really watch most movies? (Once, I'm guessing.) There are exceptions, of course (my kids have watched most Pixar movies hundreds of times), but most movies require only a single viewing, so renting makes the most sense. This reality will likely doom the high definition Blu-Ray and HD DVD formats as well. Sure, they look great. (They really, really do look great.) But these HD formats make DVD look inexpensive by comparison. The economics just don't make sense yet. They may not ever.

Personally, I've been selling off most of my purchased DVDs and turning as much as possible to digital movie viewing, either on the PC or iPod touch (while traveling) or via On Demand, iTunes/Apple TV, or Amazon Unbox/Xbox 360 on the HDTV in my living room. We also rent movies via Blockbuster. But I just don't watch individual movies enough times to justify buying them going forward. I doubt that will change, especially as more and more HD content goes digital. Your needs, of course, will vary.

Final thoughts

I regularly use both Amazon Unbox and Apple iTunes to rent movies and purchase TV shows, and both are of high quality. We watch Amazon-acquired content via the Xbox 360 in our living room, while Apple-acquired content is accessed there via an Apple TV. On the PC, either solution works well and I find both viable options when traveling with a laptop. Apple's is the only choice for the iPod touch and iPhone, and iTunes content looks great on those devices. I'm not a fan of purchasing movies with any service per se, but Apple's H.264-based movies look better than the Windows Media Video-encoded movies offered on other services for the most part. As we move towards more pervasive HD content, I'd expect Apple's choice of codec to provide further advantages, though again, the iTunes service is best suited to those who have bought into the Apple ecosystem in a big way. I do happen to use iTunes on the PC, the iPod touch and iPhone while traveling, and an Apple TV in my living room, so Apple's system is quite compatible with the gear I've chosen. If you're more firmly in the Microsoft world, Amazon is the best of the Windows-oriented services: It has the best selection, the best Web site, and the nicest PC software.