I have owned several different brands of sleds over the years and the new REV chassis by Ski Doo has turned the snomobiling world on its ear. The rider forward design is comfortable and makes average riders look like pro's.
I rented a REV 600 4 years ago in West Yellowstone and the first thing I did when I got home was to trade in my Polaris on a new REV. My 600 HO Adrenalin is as fast out of the hole as any stock 700 or 800 I have ran against and it tops out at around 105 mph.(there is an 800 model available)
The Polaris RMK's are long track sleds that are designed for climbing and it sucks on the trails.Been there done that.
The Rev is available in the Adrenaline or the Renegade package.
The renagade is a slightly longer track and is a pretty good set up if you like to get off the trail for a little powder play time...
Good luck and have fun
Scott