I find the steering to be way better on the M3 at highway speeds. Much heavier so you don't have to make as much of an effort to keep going straight. It gives a better sense of balance and control at higher speeds. It's strange because in a parking lot, the M3's steering is way lighter.
(1:40 @ Laguna Seca, 2:03 @ Thunderhill, 1:52 @ Infineon)