The facts are diesel repairs are more expensive than gasoline. Although fuel is more expensive, the mileage is usually better and your miles per dollar is less. If you tow a lighter weight RV or do not plan much time in mountain passes or higher elevations, today's gasoline engines are very capable.
However, if you do see yourself in a large heavy RV or spending time above 5000', a diesel should definitely be considered. Diesels are expensive, but making the wrong tow vehicle decision and having to replace it is even more so.
I have had many good trips with my diesel and it would be hard for me get away from that power generation at lower engine speeds. Although my current setup could be handled by today's gasoline engines, it would at the upper limits of their capacity where my 10-year old diesel still has plenty of reserve. I have had one tow due to high pressure oil fittings failing - Although the repair cost some money, people spend more on 19.5" wheels or a canopy than what it cost to get me back on the road.