I'll have to lock this one

Anyway , take a look at here since its discussed before :- http://forum.lowyat.net/topic/1001995

It depends on your usage. If you're just going to do light surfing and checking emails on the go like I do , even an iphone 2g could easily do the trick , but if you're looking for performance and you want more go for the 3GS

Read up on that thread for more info