What Mustang should I buy?

I am looking at a 2003 Mustang Mach 1. I think it would be a great buy and it has less than 25,000 miles on it. But my friends are telling me I should look for a Cobra. Can somebody please tell me which Mustang is faster an 03' Mach 1 or the Cobra. I would hate to buy the Mach 1 and find out later that the Cobra was the better car.