For the past week, I've been using an iPhone 3GS with iOS 5 as my primary handset. And when my recently ordered iPhone 4S arrives, I'll give that a similar vetting. But I have to be honest: After 15 straight months of using Windows Phone, going back to the iPhone is like going back in time, and while I appreciate that this won't make sense to those who have never gazed out beyond their sheltered iLives, I can tell you that Microsoft's smart phone OS is better, more efficient, and more beautiful to look at. Where it's lacking--and this could be a very short term issue--is in the available hardware and, more problematically, in its supporting ecosystem of services and accessories.

From a software perspective, iOS 5 is mature, stable, and somewhat attractive. (Not coincidentally, I recently reviewed iOS 5.) On the 3GS, it's also dog slow, a situation that will obviously not be the case on the iPhone 4S, which has dramatically faster innards. You tap and then wait, and just when you start to doubt you tapped anything, whatever it is you tapped finally launches. It's not a good experience, and one suspects that's completely by design. Apple, after all, has mastered the quickie obsolescence/upgrade model better than any company.

Meanwhile, Windows Phone 7.5 runs wonderfully on my year-old Samsung Focus. (I also recently reviewed Windows Phone 7.5.) Screens immediately pop to the forefront when tapped, often accompanied by a nice animation that never seems to get old. This is a system that was clearly designed with yesterday's hardware in mind, and while there are Windows Phone 7.5 features that obviously can't be used on older hardware--such as its support for dual cameras--one gets the idea that Microsoft wasn't actively obsoleting its existing customer base as does Apple. (That Apple does this while still selling the 3GS is, of course, a debate worth having.)

But it's not really the performance that bothers me with iOS 5, and as noted previously I'm sure the iPhone 4S will clear those issues up nicely. It's the usage model. Apple's mobile OS, like its desktop OS, is inscrutable. It presents a grid of icons, none of which can offer more than the dumbest heads-up that something has happened: A little red "2" on the Mail icon suggests you have two unread emails, for example, but that's all you get.

On Windows Phone, yes, we have these dumb little overlays too. And yes, the Mail tile will indeed display a little "2" when you have two unread emails. But other tiles are more descriptive, "alive with information" as Microsoft says. The Calendar tile has the title and time of your next appointment, so you can check that information without diving into the app. Third party weather apps actually display the weather forecast, so, again, you don't have to actually tap anything to find out what's happening. All across the Windows Phone ecosystem, these more intelligent apps provide you with information right from the Start screen, no navigation required.

I've used photo viewing as a canonical example of why the Windows Phone usage model--which thinks and works the way you do, not vice versa--is superior to that of the iPhone and iOS. And that's as true today as it was a year ago. If you want to view photos in iOS, you--yes, you, the user--needs to think first where those photos may reside. Are they in the Photos  app? Are they in the Facebook app? Are they in the MobileMe Gallery app? The App Store for iOS, after all, is just bursting with apps. It's the platform's single biggest selling point, as you know.

In Windows Phone, you just visit the Pictures hub. Here, all of your photos are brought together in one place, whether they're on the phone (taken with the camera or otherwise saved to the device), on Windows Live (where your camera photos can be automatically backed up, albeit in versions for sharing, not full-sized originals), on Facebook, or on Twitter. Third party photo apps also integrate into the Pictures hub, so while you could do the iOS-style "think, then search for the app" thing, you don't have to: They're all in one place.

Meanwhile, back in iOS 5, you're probably still wondering where that app is, assuming you could even remember which one it was in the first place: Thanks to multiple home screens, each with its own bizarre collection of individual icons and folders full of their own icons, that app could be anywhere. While you're looking, I'll move on.

Windows Phone is prettier than iOS. So aside from the efficiencies of its integrated experiences, it also provides a nicer look a feel, with wonderful typography, especially in those places where you'll be reading a lot of text, like the Mail app. Comparing the Windows Phone Mail app to the one in iOS is like comparing an elegant, photo realistic Dutch master's painting to a child's unwanted crayon scribbling on a wall. Yes, the latter is recognizable, and perhaps even lovable because, admit it, you have that lame, illogical relationship with the multi-billion dollar Cupertino juggernaut. But the Windows Phone version is in fact better looking. And it's more efficient too, with a better design, a superior use of onscreen real estate, and much nicer and easier-to-read fonts.

To be fair, iOS isn't without its charms. In the latest version of the software, Apple has added a nice notification system that apes the best of Android and Windows Phone and, as a result, is better than either. The "pocket to picture" capability in Windows Phone has been mostly duplicated, too, largely erasing that previous Microsoft advantage. I like that iOS 5 can now be completely PC free, whereas Windows Phone still relies, inexplicably, on the Zune PC software for something as basic as downloading photos from the device. And the iOS 5 ecosystem is simply top-notch and untouchable for the most part. What's available on Windows Phone is good, but not as good.

Where iOS really excels, of course, is with the devices on which it runs. Apple is, at heart, a mobile devices company, and its iPhone, iPod touch, iPad, and Mac laptop product lines are all highly rated and desirable. I don't have my iPhone 4S yet, but aside from a concern about the too-small screen, which makes the virtual keyboard hard to use, and the lack of an all-new design, there's little to genuinely criticize there. The current crop of Windows Phones, which date back a year, are getting long in the tooth.

Windows Phone fans, of course, are holding out for Nokia. As they should: What I've seen of the HTC and Samsung second generation devices so far is promising--dual cameras, with iPhone 4S-like resolutions--but not world beating. Like many, I'm holding out hope that Nokia will marry its incredible hardware design with high quality camera optics and Microsoft's best-of-breed mobile OS to create a device or two that can't be topped. We'll know at the end of the month, when the device(s) are launched at Nokia World. For now, this is just a hope, or a promise.

Ultimately, in using iOS regularly again, I've found something very familiar--I did, after all, use iOS for three straight years before that--and, thanks to my Windows Phone experience, something somewhat dated. I feel that Microsoft offers the best software but that Apple provides the best overall experience, thanks to the vastness of the iOS ecosystem. When it comes to hardware, right now Apple has the lead, but again Nokia could soon put Windows Phone over the top. We'll see.

In the end, iOS 5 is the safe choice, the one you recommend to less experienced users. But it is Windows Phone that occupies the innovation seat that Apple once commanded, back in 2007. If you're looking for the best aesthetics, the best efficiency, and the best software design, Windows Phone is where it's at. And that's something I suspect Apple's most ardent fans will have difficulty understanding. But look beyond your favorite platform for a moment and you will discover that the outside world is in some ways moving along faster than is Apple. And that what brought you to Apple in the first place is happening elsewhere.

Windows Phone 7.5 is quite competitive with iOS 5, and which system you choose may very well depend solely on your preferences. If prefer more apps or the safety of numbers, the iPhone and iOS is where it's at. But if you want a truly superior software experience, Windows Phone is the obvious choice. Hardware, for now, is a question mark, but I'll give Apple the temporary thumbs-up until we see what Nokia has done.

Meanwhile, I'm going to dig my AT&T SIM out of that iPhone 3GS and go back to Windows Phone. It can't happen quickly enough.