Own both. XC is very good. Assault me be the funnest sled ever. I found the Assault was the wheelie KING and as they said--No penalty on trail. Tipped rails allow max weight transfer/traction out of corners, including aforementioned wheelies. Might want to go with softer rear torsion springs option on Assault (I weigh 165) as the Assault is pretty stiff--the Indy some heavyweights say, is too soft. Suspension always needs to be dialed to rider any sled or bike--PERIOD.
Top speed is slower tho on the 144 it takes more lbs of energy to spin the track then the 129 i could ride in the deep stuff just like the 144 could grew up on sleds had a 2006 switchback 144 800 ive owned every brand of sleds started out with idk what year model arctic cat z120 when i was young then from there to a cat 05 crossfire 500 136 then to a polaris 340 touring 136 then that switchback 800 then a ski-doo 06 rev renegade 136 600 then the 14 viper 129 then a polaris indy 121 800sp now a 2010 ski-doo 1200 121inch track
Tom Cat more traction on the 137 the track would slip less then the 129 and the 137 would float more then the 129 also i think the 137 is faster then the 129 bc that extra track length
