I have a 6700 and love it. I have always been a windows mobile fan, so I may be a little biased. I tried the 700p, but couldn't stand it. Reading the reviews, many have even reverted back to the 650 after a few weeks of the 700. I will say that the 650 is an amazing phone, and if it wasn't for my need of EVDO it might have converted me to Palm.
Decide what you need and don't need. If you need EVDO, it seems your only choice is the 6700 from Sprint/VZW or the 700W from VZW. The 700p has been getting terrible reviews, even from hardcore palm users. If you don't need EVDO, I would suggest the 650, hands down. The GSM carriers have a few nice pdas, but most are WM5. Tmobile has the MDA, and if you're use to the small compact PDA, you can try the TDA.
Junkie