George, I think either way you will be happy, just make sure you do the appropriate braking and chassis mods to go along w/ any power increases on the Mustang (brakes are a necessity! the fox brakes are junk even on a stock engined car they aren't enough)
BB, have you ever even gone for a ride in a properly set up Mustang??? Honestly, a Mustang can be set up to handle much better than a Contour can, especially w/ the limited amount of parts out there for the Contour. I think the Contour is still a better all-rounder, but Mustangs are pretty fast out of the box, and cheap and easy to make faster.
George, fwiw, I am searching for a 95 Cobra to start the mod process to, (either a 351 and maybe an S/C, or an Incon twin turbo on a 5.0 stroked and poked to 331. That and I plan on doing the 3L swap too

its actually not that expensive, especially if you can do the work yourself.