I will agree with you on those things. The painted sideshirts, and new taillights on the 13/14 GT500's are better looking pieces than the ones on the 11/12 GT500's IMO. I'm just not a fan of quad tips on a Mustang, and the 13/14 wheels look a little busy, and I'm not much on dark painted wheel usually.
Another nice feature that the 13/14's have in the 15" 6 piston front brakes, and I believe 13" rear rotors.