My M3 is a 6MT. On the track, I'd be indifferent to having either that or DCT. Having DCT means you have less to divert your focus, but having manual is pretty enjoyable. You shouldn't be running into the 1st to 2nd grind issue since you'll probably be on 2nd or 3rd by the time you're out of the pit and on the track, unless you're racing from a standing start.
Yes, most of my shifts will be 3rd-to-4th or 4th-to-3rd. If I'm coming up to traffic at a sharp turn, then maybe I'll downshift to 2nd. 5th gear is pretty rare for me, but that's probably because I need to work on my exit into a straightaway.
Hope that helps.