Another factor that i think also plays into it is your weight, and what kind of gear you plan on bringing. I loved my 08 146 until there was 2-3 feet of powder or more, in bottomless powder you will notice a difference unless you are under say 160 lbs. Not sure why but you really notice the extra length when you step up to the 154 especially on the trails and around home (SK flatlands). 146 felt more like a 136 then a mountain sled, but still floats pretty decent. If you are going for the deep I would say go for the 163. I think i have more regrets about my 12 154 then I ever had with my 146, I've been doing more mountain trips lately and thought the 154 would do. When i jumped on a XM 163 I loved it, i realize this is getting a bit off topic but i think the T motion almost makes the 154 obsolete, the XM 163 seems to turn just as good or better then my XP 154 but with the floatation i was looking for.
i've been blown away at how well the 163 t does in hardcore tight stuff.
the joke on the trail is now "man i wish i had a shorter track, ha"
it does need a better front bumper, the stock one isn't the best when it comes to pushing trees down
Loved my 146. Don't let anybody tell you it's not a capable mountain sled. If you ride a LOT of super deep days then go longer. I'm always helping my 154/163 buds. If you can ride, the 146 will take you anywhere.
help them with what, working on the sled?
in deep snow a 163 will not get stuck where a 146 will be all done.