The X-Series MGMs have a 250,000 rpm limit with 2-pole motors. That means with a 6-pole motor you are limited to just over 80,000 rpm. Other than the rpm limit the number of poles doesn't matter.
My CC stuff has always run the 6 poles well but when I had MGM a couple of years back it would hiccup some with startup and braking. Not horrible and not every time but still happened and was noticeable. Hopefully they have upgraded their firmware since then to fix this.