I've read the air rides make a difference but have no personal experience. As for snowmobiles in toyhaulers.... really nice big toyhaulers, I'd invest in a snowmobile trailer. Enclosed trailers are the way to go plus you can always use the trailer for those summer day rides.
We ride in the Rocky Mountains in Montana & a lot of times the roads arent good enough to where I feel comfortable pulling my large TH up the mountain. besides the weather is usually to cold at that elevation for water so it's difficult for me to justify using my TH.
When the roads are nice & weather is warmer (usually spring riding) there can be a lot of melted snow (water) that ends up in the garage. If you clean if up right away it's ok. But over time it may present problems. There's nothing better though, than sledding back to your TH.
Also keep in mind that the track can tear up the garage floor.