I came from a 9700 to a g2 (both tmobile). I was once a hardcore believer in the physical keyboard, so I decided if I went android I would choose the g2. After a while with the g2's physical keyboard it really wasn't growing on me, and I thought I would go back to the 9700. I then decided to learn the touch keyboard and realized how amazing predictive text is. It didn't take long until I was typing 2 to 3 times faster than I ever did on my 9700.
I still get use out of physical keyboard when I need to input a username and password or type in a web address that isn't in the phone's dictionary. As far as functionality between the phones and the speed of 4g network, there is no comparison. Everthing I loved about my blackberry I found in app form from the market.