Nothing will take advantage of the dual core chips yet, by the time things are coded for it, your 1 year contract will be over and you can get a new phone. Although I prefer no contract and just buy my phones outright.
Honestly as cool as the dual core is, you wont see any increase in speed over what the thunderbolt has until programs are made to take advantage of the dual core ability. So if they are otherwise similar, I'd choose the TB over the Bionic any day. Better chassis design (opinion), more RAM, 32GB SD card pre installed, Sense vs Blur, and no eFuse.