The new edge is no longer in the spotlight with all the new mustangs on the road now.... in fact it's fading fast where I live. The 5.0 is going to keep that trend going while putting down some really big numbers that will eat up that 2007 GT. IMHO that is two reasons to go with the Cobra.
If you are only considering the '01 snake or the '07 GT, definitely get the '07 GT because it's almost certain that a 5 owner cobra has been whored around (unless you don't mind not knowing its previous history, etc).
BUUUUUT, if you were considering a GT, I'd wait around to score a new '11 Mustang GT (if it's in the budget). Those things look very promising with the new hp/tq numbers.