I think Cobras get lumped into AS, at least the 03 cobras, and you cant get one for under 22k yet either. I would do the Bullit over the Mach 1. Im pretty sure it has a better factory suspension aka slightly stiffer than the Mach 1. And if warranty is a concern you are better off getting an 04 Mach 1 or 04 GT. Anything else is too old and wont have one unless for some crazy reason you can find a low mile 02 Camaro.
The previous gen Mustang you can get dirt now since they are moving them out for the new generation. You can pick up a 98-00 Z28 camaro really damn cheap, probably 10k or under easy.
I love my mustang, but the Camaro has a better setup to start with from the factory.