I have a 36' Foretravel motor home with 350HP pusher diesel. Boat is 26 eliminator. So far this year I have gone 5000+ miles going to differenet lakes.
Advantages are going to different lakes & surroundings. You have to pick where you pull into. Some places I have a hard time moving the package around. When we stopped at Sam's Place in Vegas It took a while to get boat & motorhome on site. Launching boat with MH is only a problem if area does not have enought room to get turned around. I have asked people at camp sites if they would launch boat & most are happy to do it.
When I get a new motor home I will go back to a 36'. As far as a 31-35' boat, I do not know if I could get around to some of the places I go with that long of a boat. The problem is turns & places to stop. State laws have overall lenght limits so you have to watch out for that.