I think the real difference, is that you will fill the full impact of the heaves on the house. When towing, you're insulated to what is going on in the house as it is working it's way over/down/twisted/abused but he heaves
I noticed many a Fiver go flying by me at say 30-35 MPH, while I would be slowing down to between 5-10 to work my way over a bad stretch if ice heaves. Think of Destruction Bay area, at least that was the longest day of the ice heaves for us in 2014. (We crossed the border to Canada 5/1, so were a bit earlier then many. And, not all of the ice heaves were red flagged yet...).
So, the main difference to you in a 40', is to slow down more. I don't thing the damage difference between a Fiver/Trailer is any difference then a Class A. Well, probably not true, lots more weight usually associated to the bigger Class A's. I think I can remember at least three times, that after a Fiver would fly by us in a rough stretch. I'd see them on the side with problems later on. I also remember while in Tok, the RV Park Owner commented the one of the most common questions he had, was 'Who can help me with my suspension, I broke (Fill in the item broke here.). He said this was usually from a Fiver/Trailer, vs a Class A. (Again, not because they're any less susceptible to damage. But since you hear the strain on the house, it helps you slow down...).
Just my opinion, and others may have a different one