I actually have both a VitaMix and a Blendtec. We had the Vitamix first, and just decided to swtich for the second blender on steroids which we purchased. Both function fine. One thing about the Blendtec is that it's shorter and fits under the cabinet, the Vitamix does not. I don't think you could go wrong with either one. I'd just research to find which deal is better (I think Costco may carry both. I am not sure on specific models though).
I haven't forked over the money, but a source that I trust very much (Joe Rogan at Onnit.com) switched from selling Vitamix exclusively to selling Blendtec exclusively.
Vitamix has a ton of good, free recipes on their website. I'll be purchasing a Blendtec soon.