I worked at Tropical Smoothie Cafe where we used Vitamix, so I was sort of leaning towards that based on my experience. However, after cursory research (would have done more if I hadn't been so experienced with the VM from work) I basically looked for the best price on either model and ended up with the vitamix.
The things I hear mentioned that I would look at/consider are:
1) height....would be nice to fit under cabinet. Not a dealbreaker for me, but I do see it as a big pro for BT.
2) Warranty....are both comparable? Not sure
3) Tamper....I like having it. My experience is that if you are good at recipes, tamper may not be needed. I tend to totally wing it, dumping it random quantities. I often use the tamper and can't quite imagine not having one. YMMV of course. We didn't even have tampers at the restaurant so it obviously worked fine then.
4) Wet/dry....not sure? I haven't really planned to use it for dry stuff at this stage in my life anyway.
So for me, I just found the best deal I could and wound up with a Vitamix from craigslist and we do use it all the time and love it.