The Polaris "Gripper" is great on the M series. I have the SLP "Mohawk" on the other sled and like them also. I ran the SLP Powder Pro for 6 years before giving the Gripper a try. I'm liking the Grippers.
I installed the grippers last year. They are a great ski. I just bought a sled that has powder pros, I've never ran powder pros. I think I'm going to sale them and put grippers on it.