(You realize that you have asked essentially the same question in two places? So expect answers in two places.)

We had a gas motorhome for a while and it worked fine. Now we have a diesel pusher and it is better, but more expensive with a retail price about double the gas. It does take the hills better, but our gas would pass older diesels going up hill. It has better insulation, but that is because it is higher end. The ride is better because of air bags, but the gas ride was good. Our gas rode better than many other gas ones since we spent about $3K on suspension upgrades, way less than a diesel upgrade. We have friends who are driving old gas motorhomes, including GMC ones from the 1970s, and they are still running.

There are junk diesels, there are junk gas motorhomes, ones that will look tired in 5 years and worn out in 10. Don't overspend on your RV if the money is important to you. Think how you will use it and decide if the $50K minimum price increase for new diesel is worth it to you. $50K is probably low. Check carrying capacity, you need 2,000 to 3,000 lbs as a fulltime couple for your stuff, after the water, fuel and your bodies are included. There are gas and diesel motorhomes that a full refrigerator will overload.

35' and below most diesels have too much rear overhang, you will need suspension upgrades to have a decent ride. Unless you buy a used 32' Country Coach, they did the upgrades and the ride was good. 37' or longer I would go with diesel, the chassis weight will eat up your carrying capacity since most gas motorhomes are 22,000lb chassis, though some go to 25,500.