28 will lay waste to a stock 04GT
and its gonna stay that way as long as both were modded equally
but not to shaft the mustang, most would consider it a more reliable vehicle, easier to live with on a day to day basis (if thats even important) and you'll definately feel like a better part of society

meaning that youre less prone to suddenly have an urge to buy a trailor if you have the mustang
(oh, and i think a 04GT+supercharger is gonna be alot more than a 02Z28)