As far as the tipped rails go, clearly they help in snow that is packed down, where the longer track sleds will push the hardest. So since it doesn't hurt to have the tipped rails at all in the powder, why not keep them?? Polaris moves away from the switchback original design with 144 and tipped rails to 136 coupled suspension, and no tipped rails....and about the same time yamaha goes longer form 136 to 144 and tips the rails.
Bunch of monkey see, monkey do processing...aka, reverse engineering by the design teams.
Tipped rails help the sled turn on trails...in powder it doesnt hurt or matter. Longer tracks are much better in the powder than short tracks. But I believe the single biggest difference in moving thru powder is the lug size.
Having had everything from 3/4 inch lugs to 2 inch lugs, I would tell you that the longer lug is by far the best in powder but really doesn't seem to hurt much on trail work unless the trail is very packed.
Going with longer lugs as they are found on the powder sleds nowadays, means that the makers realize that longer lugs help in powder too.
I would NOT buy a sled that does NOT have at least the 2 inch lugs, UNLESS you run thru lots of rocks and stumps where a hard spin on one of those things can knock lugs off the track.
For this reason, I believe that a 2 inch lug track is about optimum in all but icey conditions. It works well on trail, and far better off trail. If I was going thru boundless powder like they get out west, I would buy the longest track sled I can find and get the longest lug track they make. I would also improve the heavy front end of any powder sled by putting the widest skis I can find on it. Doing so means you float over rather than plow thru the snow....making steering easier.
So go long my son.....in lug height and track length and you won't look back. If you are going to lake race, perhaps this would not be as wise, but for everything else....that is what I would recommend to anyone.