Tony, the newer models have blocks on the side of the rails to help keep everything inline while traveling through the motion. I don't know if it completely eliminates it, BUT I do know it helps keep things way more under control then the skids of old. Everything up until the '14 skids without these i couldnt beleive how much the tips of the rails wander. skid tails, etc.
ON the note of just skid vs skid. I had the pleasure of riding two identical turbo XM's with each skid underneath. Both purely out of the box settings on the shocks. here is my brief overview after a few hours of riding both of them.
First off, they both handle 10x nicer then stock. the better shocks just soak up the bumps. it was a 10 mile trail in with some good 1' deep chatter bumps and I was amazed at how much faster i could ride on both without getting chucked around.
Ezryde-
-soaked up the deeper bumps better, you just dont feel them.
- very playful front of the sled while maintaining good ski control.
-rides slightly down in the shock stroke allowing it to drop into holes well.
-blasting through hard packed wind lips this thing is a dream, no wonder so many race guys run it.
-on hard snow its definitely my favorite suspension
KMOD
-excellent ski lift control (depending on coupler setting)
-great improvement over stock when hitting bumps of all size.
-rides at full height, seems to stay out of the snow a little higher which is favorable for powder riding
-when coupled to the lowest setting it seem to do re-entry style maneuvers with much less effot
-for deep powder the kmod definately takes the cake.
As for durability, they are definately two of the strongest skids, Both of them are rigid as can be and very well though out and strength and durability comes above pure light weight in the design. I would not desitate to buy either one, But my choice would be made by what my riding goal was with the sled.