Basically a bigger end can (more internal volume) allows you to run a straight through exhaust without really excessive noise. The small end cans will make similar power with the baffle removed but will lose out to a larger can with the baffle in as the baffle needs to be more restrictive to keep the noise down.
Assuming you are keeping the standard headers the length of the mid pipe also affects where the power is made. The longer it is the more you loose at the top and the more you gain in the mid range.
Horses for courses really, decide on looks / power and where you want that power, how much do you want to pay, how much noise do you want to make etc etc.
I haven't seen any test recently, but the small cans fully baffled to meet noise regs can actually lose a fair bit of power.