I've been doing some research on that is very exact topic. And a simple answer is no they do not cross over.
The not so simple answer is it really depends on which sled you're talking about. Myself I'm looking for a better seat for my 13 SBA. Something that is taller and more firm and I don't know which one to get yet. Right now the toss-up is between the lightweight RMK seat and the premium Mountain seat. But I don't know which one will suit my needs better.