Mustang understeers like a boat and isn't fun to me. I chose the Skippy when I was going from rookie -> Class D and then went to the Star Mazda. I still race both to this day while I'm running the higher class series. Jetta is hard to find official races in, Mustang fits some peoples interests and the Skippy fits some peoples interests. If you like understeer go with the Mustang, if you want to drive it harder and slide a bit, go with the Skippy.