I rode polaris switchback assaults the last 2 seasons and bought a 2012 summit x this season when I moved out west. Picked it mainly for reliability. Money was tight and didnt want to buy a polaris and have to do a motor right away... Also wanted to try something different and all the guys I ride with here have the same sled so figured it was a safe bet.
Sled has been great so far. Have ridded 4-500 miles this season. 10 or 12 afternoons of riding. Really good on fuel and oil. This has the S36 handling package but is not as tippy as I would like. It feels similar to my 08 renegade, engineered to ride flat but is willing to tip when theres lots of snow. Most days this year has been fine as we usually only ride when it dumps so I haven't had any problems manoeuvreing it. Last ride the snow was windblown and firm and at one point we had to side hill for a mile or so to get down the back of this mountain. Couldnt get the sled to roll over for the life of me, and I'm 175 pounds and fairly good rider. It just doesnt want to sidehill unless theres 8-10 or more inches of soft snow. Compare it to a polaris chasis where you can roll it over in 4 inches of snow on a lake with a little effort. Also when on a sidehill this sled constantly wants to turn uphill, I have tried moving my weight further foreword with no luck.
I highly recommend the sled as it has been extremely reliable, tonnes of power, just add gas and go. However if your doing more riding in tighter trees where you actually have to get places I think the polaris is a little easier to throw around. I have only ever ridden polaris back home in the prairies and this summit out west so its a tough comparison but I might get an RMK next year to compare.