Each has its pros and cons but ultimately the iPhone's iOS is superior. Especially because it is updating to iOS5 very soon!

I've trying android and it was not a good experience at all I really don't recomment it, blackberry is only good if a lot of your friends have it so you can use "BBM". But if you want the 'Ultimate' phone definately go with the iPhone. The iOS is very fast and crisp and there is no lag or slow time at all. Also there literally is an app for everything.

Hope this helps!