Crossovers are supposed to bridge the bumps better, but riders are concerned about ease of handling and cornering on the trail. Here's one way to evaluate the difference between sleds: Measure the difference in how much track is actually on the ground on a short-tracked sled vs. a 136" crossover. You might be surprised at how little difference there is. Some crossover skids have the rear of the rails tipped up, so you have less track on the ground when on a hard-packed trail, but more flotation in deep snow when the tipped rails are in contact with the snow off-trail. Also look at weight difference between the 121 and 136, 141, etc. Some of the crossovers come with a 1.25" lugs standard, which is nice.