I'm probably speaking out of turn, because I've never owned a MH, but I've done a lot of research lately, so here goes.
I just ordered a new gasser, and I will tell you why.
We don't need to tow anything but a toad.
I don't like the "junk" that they have put on these diesel engines of late. They are choking them in the name of no soot and less NOx. Then, they are making us spray urea into the exhaust to remove more NOx. The government now makes fuel suppliers take out sulphur and thus, lubricants. They then have to add other lubricity back into the fuel. The price difference between gas and diesel is never going to flip-flop back. Shame, though. Diesel was the best available fuel for moving large masses down the road efficiently. It took the government to screw that up.
Thus, another vote to go older. You will see the older coaches will need some updating, though. Many will have old tube-type TVs. The upholstery may be dated or worn, etc... The money you save going older will dwarf the amount you will put unto it for updating.
An older diesel was one of our options when we started our research. We chose to go new and gas for the reasons above and some others not relevant to your search.
Good luck