Another difference is that you can go to a contest in a 30MPG Ford Focus and still have a top-of-the-line plane in your car, ready to dominate the skies in Pattern. With IMAC, it usually also requires a trailer or large SUV...
Funny, though, a top-level 2M pattern plane will cost nearly as much as a top-level 40% IMAC plane.
Still, if there were more than 2-3 pattern contests within 350 miles of me I'd have a pattern plane as well.