I guess it all depends upon what you really want. In my mind the Crossfire and the Mustang are not similar cars in the least. The Crossfire is American/German designed European semi-exotic sports car that can be had at a very reasonable price. A Mustang is simply the latest iteration of an American pony car, and not badly done. I know it was just my personal preference, but I didn't even consider a Mustang when I shopped for the Crossfire. I was looking more at BMW Z3/4s. Mercedes SLKs and the occasional Porsche Boxster. Too me, in value, performance and style/design the Crossfire won out over them hands down. Clearly I was shopping content rather than badging.
Do I like my Crossfire Coupe? I absolutely love it, as much as my XKE. Would I trade my 2004 Crossfire with 16K miles even up for a new Mustang? Not a chance.

(Unless of course it would be to sell it and buy another Crossfire and keep the profit).