I thought the same thing... but I think there were a few things that caused it.
Mustang was heavier
Gear ratios were taller, especially the rear end so even with the extra torque, it seemed more composed.
Longer wheel base with the Mustang so when the rear did kick out, it's easier to correct.
Much wider tires on the Mustang. 295's in the rear, 275's up front, vs. my 205's all around.
~200 whp (on a Mustang dyno) in a 2400 lb car with a short wheel base and sub-par tires. Yeah... scares me. LOL.
I had the opportunity to buy that SVT. Liked the car, but kinda glad I passed on it. I'd rather have a 2010+