Seems newer RVs are having more issues than older ones. I bought a 2007 Montana 5th Wheel new and kept it 14 years and it could not have been more trouble free. Not sure that can be said about any newer RV of any type. I like to buy new. But finding a several year old unit in great shape would certainly be worth considering.
With motor homes, you have the additional issues of a another drive train to service and maintain. And you would probably want a vehicle that can be towed behind it if yours is not towable.
With a travel trailer, you need a vehicle capable of towing whatever size travel trailer you decide to buy. That may mean buying a new tow vehicle.
You just need to decide what is right for you.