They offer many similar capabilities (email, web browsing, multimedia, gaming, etc.) but they do it with tools designed to be used single-handed, with just your fingers (and with multiple fingers), quickly, and only offering the features that work well within those constraints.
They also don’t focus on large application suites that offer every possible feature for things like text formatting, photo editing, file management, and so on. Instead both iOS and Android break down complex desktop-oriented tasks into more basic forms that are appropriate to the device’s size and form factor as well as to its primary input methods.
Some times these are somewhat scaled down versions of desktop apps (such as text editors or word processors that focus on text entry, basic formatting, and image placement – which are all many people do in such tools anyway).
Other times specific tasks are broken out into separate discrete apps (like photo editors that focus just on color correction and red-eye reduction or photo viewers that offer no editing features but display sharp looking slideshows, turning the tablet into a digital picture frame). In either case, the OS itself and the apps are designed around how people relate to mobile devices and how they use them differently than PCs.
This is a reason that I think Microsoft is making a mistake by sticking solely with Windows 7 on tablets. Windows Phone 7’s interface has a lot of really good things going for it including the Start screen, which I think is a great revolution in smartphone interface design. Unlike iOS or Android, which required some serious tweaks to go from smartphone to tablet (iOS accomplished this when the iPad launched, Android will get there with Honeycomb), Windows Phone 7’s swipe to see more content approach could easily scale to a variety of form factors and resolutions – and would look really good on a tablet.
Does this mean, I’m against the idea of Windows 7 tablets entirely? They’ve existed as a niche market for a while and will probably continue to do so. For some people, who really want a whole PC in that form factor, they’ll be appealing. PCs like