Ive owned an M6 and am now on my second e92 M3. The M6 was faster 3 gear and above vs my DCT M3. The SMG tranny on the M6 however ruined the whole car for me. I never drove a 6MT with the V10 but imagine thats the ticket though...
Oh and there is no question, the M3 is a million times more fun to drive and I would rather have one any day of the week. ( Again, this is coming from someone who owned both)