My surgeon said he didn't know until he had me under during surgery. It depends on the size and shape of your stomach. My understanding is the lapband is larger and holds more CCs. I was given the realize band. As best I know, they both function the same.
I have never been able to tell a difference at all after doing lots of reading and asking. I think they are the same thing, just manufactured by a different company. My surgeon only used the Realize Band, but he promised it was not because it was "better or worse" it was just the contract the hospital had. Good luck with whatever choice you make!