With all five models of Surface Pro 3 now shipping in the US and Canada, we're going to start getting some answers about how each differs. Obviously, the various models get more expensive as you move up from an Intel Core i3 processor to an i5 and then an i7. But how do these upgrades impact performance, battery life, heat and fan noise, and other important metrics?

For the moment, most of the information we have about these differences comes from Microsoft, which acknowledged the availability of the entire Surface Pro 3 range in the US and Canada in a post to the Surface Blog.

"Surface Pro 3 is the first generation of Surface Pro for which we've offered this range of configurations," Panos Panay explains. "We did this to so that our customers could decide which Surface Pro 3 is right for them. This is the tablet that can replace your laptop, and we know that laptops and tablets are used differently by different people. The new range of products accommodates this with a different processor, memory and storage of options and price points."

Right, we know all that. What we're curious about is how each processor upgrade in particular—but also the RAM and storage changes we see in the higher-end versions—changes the overall story for Surface Pro 3. Here, Microsoft only offers some vague guidance.

Core i3 model. Panay says that the base Core i3-based Surface Pro 3 model ($799 plus Type Cover) "is one of the fastest Core i3 devices available," but is aimed at "customers who want the versatility of a Surface Pro 3 but who don't run the most demanding applications or workloads." He recommends this version to students (for note-taking and web-based research) and for "anyone [who] wants a very portable device to be productive on the go, run Office and other desktop applications, make Skype calls, watch video, and casual gaming."

Core i5 models. The mid-level Surface Pro 3 models ($999, $1299 plus Type Cover) should satisfy the needs of most users, providing "the power and efficiency to be productive across a huge range of activities ... This machine outperformed any laptop I've used, and it will be the machine of choice for a lot of our customers." I'm using the $1299 version (8 GB of RAM/256 GB SSD) and find the performance to be just fine, though as I've noted the fan does kick in if you really press the machine.

Core i7 models. Of most interest to power users and the well-heeled, the Core i7-based Surface Pro 3 models ($1549, $1949 plus Type Cover) is "the most powerful Surface [Microsoft] has ever released" and is "designed to provide the power that [its] most demanding customers need." Panay specifically says that these Surface Pro 3 models will be "brilliant" for photo, video, or music editing, and they are aimed at scenarios as diverse as "connected to multiple monitors and peripherals or travelling."

Ultimately, Microsoft doesn't offer a lot in the way of real-world buying advice, however.

"You'll decide which Surface Pro 3 is right for you – whether it is high performance or great capabilities for web browsing and working in Office," Panay notes. "You'll balance this with what you want to spend. You'll think about how the machine looks, how solid and reliable it feels, and how it's going to help you accomplish the specific things you do or plan to do."

I'd love to offer some further insights into this decision, but I don't have Core i3 or Core i5 models to test. But I'm starting to collect some reader reactions to their new Surface Pro 3s, and am particularly curious about these low- and high-end versions in particular. For example, does the i3-based Surface Pro 3 perform acceptably, and is there any battery life advantage to such a machine? And on the high-end, do the i7-based Surface Pro 3 models run hot and drive the fans too often? Does the extra performance come with a sacrifice in battery life?

I've only heard from a handful of i7-based Surface Pro 3 users so far, and the consensus, sadly, is that these machines do indeed run very hot, particularly in the area near the upper right of the screen. I've not heard from any i3-based users yet. If you did get a Surface Pro 3—especially an i3- or i7-based version—please let me know what you're seeing.

I was also hoping to see what others were reporting elsewhere on the web, but I haven't found any resources related to testing the different versions side-by-side. Anyone?