The floodgates are about to open for Honeycomb tablets, and so far they all have 10-inch screens which are less mobile than 7-inchers. Based on my hands-on experience with Honeycomb, I suspect the reason for the bigger screens is necessity. Honeycomb is an attractive interface that is well-designed for touch operation, but it puts so much on the screen at once that a bigger display is required. It also makes the main home screen very busy, and in that regard tablets with Froyo may be better for serious work.
Don't get me wrong, I was very impressed with Honeycomb during a recent session with the Motorola XOOM. It does so many things well that it is a serious platform for tablets. The issue I have with it is the lack of focus for the task at hand. Both iOS and Froyo excel at keeping the user's focus on the single task at hand, which is a very good thing for a handheld operating system. Tablets by design have the user's attention as they are used in the hand, and that task-oriented work is handled well by Froyo and iOS.
Honeycomb is so buy on the tablet screen that it doesn't grab the user's attention for doing things. It presents so many things on the screen at once, in an admittedly gorgeous way, that it doesn't lend itself well to focusing on tasks. There is so much grabbing the user's attention that is seems to require a lot of swiping left and right, up and down to get things happening. It may become intuitive over time, but the desktop metaphor used by Honeycomb is less like a mobile platform and more like a full computing environment.
No doubt some folks will like the desktop environment, but I believe it will take a longer learning curve to get more proficient with Honeycomb than with Froyo. The older version of Android presents things in a simple way on the home screen and applications screen, and a simple tap fires up the one task on the entire display. The user's focus is then on the task at hand, and not the pretty interface.
I hope I am proven wrong when Honeycomb-based tablets hit the market, and I get serious time using them. The OS looks sweet, and perhaps with a little practice it will become second nature to use and get things done. It will be a shame if Honeycomb remains harder to use than Froyo or iOS after a short interval of using the tablets.