Bare has basically 3 lines of wetsuits. The Sport, the Velocity and the Elastek. The sport being the entry level suit, the Velocity being the mid range one and the Elastek being the top range suit. Some options and colours like having a Tall or Short sized wetsuits are only available in the Velocity and Elastek lines.
Sport line: It's a good suit with good seams. The material used is a lot stiffer than the Velocity or Elastek lines. Great suit if you don't want or can't spend too much.
Velocity line: Best bang for your buck. More stretchy than the sport, although not as much as the Elastek. Available short and tall sizing options. Cut slightly different so may be more comfortable when bending your knees and elbows.
Elastek line: This is Bare's top line. Even more stetchy material than the velocity and the finish is different inside, making smoother and more comfy. I believe, depending on the thickness of the suit, that you also get the added benefit of having neoprene bands sewn in the wrist and ankle area of the suit to act as seals to prevent too much water from coming in the suit and cooling you down too much.
That's off the top of my head. I'm pretty sure this info is correct.