I'd take lug depth. If you have a 2010 switchback that is a 136 right? I'd just put a 2" track and gear it down somewhere at least in between stock and what an RMK is, or closer to RMK, and keep it (unless you just NEED to have a new sled). Two reasons, first with a big lug track there is a lot more drag and you won't be able to even pull the stock gear anymore and second you need to be geared down more for boondocking and stuff so you can creep along better. Narrowing the stance would be helpful in making it lay over better but not required. Unless you are out west in seriously bottomless pow track length is not super important, at least not in the UP 90+% of the time. If it really was you would see more guys running 160+ tracks. Having a deep lug to really move the snow when going anywhere other than level terrain is better. I guess to "prove" my point, if I was going riding and had the choice between only a 136x1.75" or 144x1.25", i'd take the shorter 1.75" for sure and I bet most all boondocker types would agree. Now if the choice were 121x2" or 150+x1.25" then it would get tougher because you are getting onto a huge change there.
I ride with a guy that has a 136x2" 800 Renegade and it does just fine in the UP and I never hear any "if only my track was longer" type comments.
Realize though in my opinion (that's what all of this is right?) you really give up a bunch of the trailability of the sled going at or over a 1.75" lug. That's just my opinion but it starts to take lots of power to just turn the big thing and you start losing speed, any sort of hard pack trail and wasting away hyfax better be in your mind, and finally you start to get a lot more vibration. That's not to say I can't or won't ride the trail with my 153x2.125" M8 but it is a compromise. A compromise I am willing to make as I ride off trail 80+% of the time. But if you ride the trail better than 50% of the time i'd stay 1.5" lug or less and compromise for the trail end.
