Well to be honest, they're both so similar in terms of ease of use and slickness of interface that it's hard to make a case for either really. The iphone is definitely a little "slicker" in it's look and feel. However, with Android you're not subject to Apple's whimsy in terms of how your phone looks and what you can do with it.
As for the "There's an App for that" adverts, they lie. Just about every app you can get on the iphone store you can also get on the android market, usually for free.
i'd say really it's about personal taste, have a look but if you prefer the iphone's interface i'd stick with it really.
The g2 is meant to be a stupidly good phone for the android OS to work on so i'd go into a T-Mob shop and have a looksy ;o)