I would definitely go LTE!
Bottom line is you're stuck w/your choice for 2 years or so but VZW is working pretty aggressively to upgrade their network city by city. LTE phones speak 3G just fine, and will work fine in that context. Admittedly the battery life might not be quite as good as a regular 3G phone but when you either visit an LTE city or when LTE comes, your'e good to go.
The Bionic and all the current generation LTE phones are all transition phones. They can talk to the old and the new, same as my old T720 and v710 were. Eventually though, we'll be full LTE everywhere and VZW will start selling phones with only LTE radios in it.
If cost is a major factor, the X2 isn't a bad choice, but that's really the ONLY thing I would put in its column.