This was discussed a little here:
http://www.chiefdelphi.com/forums/sh...hlight=battery
I think what you will find is that they are all nearly identical, otherwise they wouldn't all be legal. That would provide an unfair advantage to a team that can afford the better batteries. Every single one will provide you the power you need for 2 minutes and 30 seconds.
Now depending on how much load you put on it, you may be able to drain them pretty quick. But if you remain in, or near, the batteries spec sheets (which can be found by searching the specific battery on the manufacturers website) amp hour rating everything should be just fine.