I loved having the 5 row keyboard on the G1. I could use console emulators to play NES, gameboy, genesis, SNES, etc games. Email was super fast and error-free. But the battery was bad enough to negate those. It wouldn't last a single day, not even with all the GPS/bluetooth/wifi disabled. You can play some of the emulators with just a touchscreen like the MyTouch, but for my casual usage it's not a worthwhile experience. At first the battery lasted easily 2 days on a single charge but with facebook and twitter notifications it went down to about 1.5 so I now charge it every night. It could stand to use more memory. Enter the Fender edition MyTouch which has ~90 MB more memory. I haven't had any hands-on with it but it has been confirmed to be receiving an update to android 2.1 in Spring (the regular MyTouch has received no confirmation either for or against an upgrade). Overall I'm very happy with my MyTouch. I'm disappointed about the memory but not enough to not recommend it. If you really don't like the look of the Fender edition or don't want to pay the extra then it's a great choice. I tried the Cliq and the Behold in store and I hated their screens. The Cliq has the extra UI layer on top of android to add a bunch of social networking integration but I thought it was too much clutter for not enough gain. The Behold just looked weird, almost like it was a fake display screen. And they also have a custom UI on top android that I didn't like.
So in conclusion I say the MyTouch. Go for the Fender if you don't mind the extra cost and case design as you get extra memory and know it will receive the OS update.