I faced a similar choice. Have been pretty happy on T-mobile with my 7100T.
Thought I might "upgrade" to the Motorola Q just introduced on Verizon.
Referred to as RazrBerry, BlackBerry Killer.... hmmm not really.
Basic features, very thin profile, camera, nice multimedia(audio and video), ultra fast CDMA/EVDO network, QWERTY keyboard, pretty nice design and about $200 from Verizon if you sign up for one of their unlimited data plans STARTING at $79/mo for 450mins/unlimited data.
What really turned me off however.
Verizon $20 more per month for considerably less.
No "real" push email. For email not located on an Exchange
they have a kludgy "wireless sync" that polls your email boxes every
15 mins , sends an SMS message to the Q to fetch ur email.
The microsoft patch needed for alleged "real push" with exchange not
implemented as yet.
Tethering is additional charge as are SMS/MMS messages on the
unlimited data plan..
Windows Mobile SmartPhone V5 does require periodic "reboots".
Battery life for WM5 devices is a day or so.
So after all that, I ordered a an 8700g for $200( upgrade 2 yr), and will
stick with my current "minutes & mail plan" for $60. I'll get my instant
push email, a stable os, fast browsing on the edge network, and
good battery life.
Don't regret it a bit.