I would go with the Magnaflow, for some reason Flowmaster just doesn't sound like it belongs on a crossfire.

I had flowmasters on my Chevelle and those are the only cars I would even bolt them to, good for any American muscle car.

I bet the magnaflow has a better sound but I'm just guessing. Also the Flow master's a very heavy mufflers, made from 1/8" thick steel, not my choice for a sports car, you want something lighter in weight then a Flowmaster.