Easily the iPhone 4S, blackberry is a dying platform. The iPhone have a better OS and it also has the largest selection of media and apps. It will also hold its resale value way better if you decide to sell it later on down the road.
Depends... If a lot of your friends have blackberrys then get the bold because of blackberry messenger (free messages between people with blackberrys) if not then an iPhone 4s because the apps are better and its good for storing music etc.