Generally, the DP chassis will have a larger wheel turn angle, so they are surprisingly agile. I have not seen your roads, but a few things to consider.
A longer wheelbase DP will be more stable on the highway than a shorter wheelbase, all other things being equal.
The longer you live in the motorhome, the more often you wish you had a little more floor space. If you can get a 38 to 40 ft DP up those roads, you'll have a more living and storage space. The fuel mileage will not be that much different.
Drive as many motorhomes as possible. You will be surprised at how well some handle, and how poorly some handle. Try to test drive in crosswinds, or on the interstate with big trucks passing you.
Good luck with your search.
Fred