I have a HTC 6800 right now.
I also own a HTC Touch, but switched out of it so I'll post both.
I went with the HTC 6800 due to the slide out keyboard. It has a bit more power than the previous HTC 6700, and the magnetic slide on the keyboard felt less "clunky" than the 6700.
I went with it over the HTC Touch due to the keyboard, and the fact I was able to activate GPS (which is disabled on Alltel for 3rd party apps) with a simple file update. I have added the HTC Home plugin, IContact for the address book, and an upgraded GPS app (on top of the official ROM) that works with the various GPS capable programs.
The HTC Touch was great, but the lack of a keyboard threw me off. I liked the on screen keyboard, but I liked the feel of buttons. Plus the GPS was harder to unlock and didn't feel like dealing with it.