I've had Windows Mobile 6.5 phone, Android phones, and iPhone.
Except the WinMo, Android and iPhone are pretty similar. WinMo was so bad, I didn't even give Windows Phone 7 OS a shot.
I've played with the Torch for a day and don't prefer it.
iPhone has many apps to help with being on top of things, but Android has most of those apps too.
Both iPhone and Android have great browsers, for some reason the Android browser will be able to pull up some flash pages but will end up not being able to connect to some url strings.
I particularly look for the apps when choosing the phone, the productivity tools like to-do lists and calendar and sync.
iPhone has a pretty nice email interface now that threads conversations so you don't get confused about what the discussion is about.
iPhone 4 has the clearest screen by far.
Android has Swype so you can type pretty fast without a keyboard.
If you need a keyboard, those Motorola Droids have great keyboards, Blackberry still has the best keyboards hands down, but their OS/Browser/Build Quality have been lacking for the past few years.