For your planned shorter term ownership, I would not get too hung up between Gas vs DP. And as this will be your home for that period of time, I'd look at the 34-36' lengths. The Bounder's you have listed are a well known Bread & Butter RV, and would have higher ease of reselling when the time comes. Most of these should be on the Ford F53 platform, and I'd look for a 2006 or newer. (But validate, as some early 2006 models, could have 2005 4spd chassis.).
I'd also add the National brand, the Dolphin was a nicely built and appointed RV. And they came in both the F53 and Workhorse chassis. Either one would be good. The 8.1 in the Workhorse chassis is a little quieter while climbing mountains.
For your intended usage, you will find very few limitations with a 36' and under rig. A few sites may not work for you in some parks, but we frequently go to parks with a max of 36' limits. Drive our Toad around to scout out sites, an very seldom do not find a location that we can fit our 40' Diesel Pusher.
If you decide to go the Diesel route, I'd suggest the Winneabogo Journey and sister coach Itasca Meridian. They come in 34-36' lengths, usually with a CAT C7 - which is plenty of power for that size. And again, these are lengths and coaches that should be easier to sell when the time comes.
Toss in Newmar Dutchstar and Meridian, which had some 36' gas models.
And Alpine made a very nice 34-36' Diesel Pusher. They're more in demand, and move fast when they become available. IMO, of all of the coaches mentioned in your, or even my added units to - the Alpine on the Peak chassis would be the best handling of them all.
More important then specific make and model, is finding a gently used coach that fits your budget. If you are not buying in person, I'd suggest you budget funds for an independent inspection by a second party to review your potential purchases. Pictures are nice, but hey do not always show the reality of condition of a rig.
Happy hunting, and have a blast!!
Smitty