For class A motorhomes, there are a lot of differences than just fuel that typically go with gas vs. diesel, some of which are of far more importance than the actual engine differences.
Gas class A's are basically all front engine units, with what amounts to a truck chassis (leaf springs, etc.). Diesel class A's are basically all rear engine units, usually with an air suspension, more like a transit bus. Having the engine in the rear unsurprisingly makes for quieter cockpit, and the air suspension makes for a smoother ride.
Diesel class A's also tend to be fancier and higher-end (and more expensive) in other areas than just drivetrain--fancier furnishings and systems, better finishes and fabrics and floor coverings, that sort of thing.
I suspect most would agree that the diesel pusher is a more comfortable and generally preferable setup. Whether it's better for you is something you'd have to figure out. The maintenance costs tend to be somewhat higher for the diesels, not necessarily due to the engine differences (or not due to them alone) but also because they have larger and more expensive tires (and possibly more wheels with tires), and more complicated systems, etc.
Towing a car four down is generally less annoyance than using a trailer. If you do tow with a trailer, consider installing a trailer hitch on the car so you can reposition the (empty) trailer in the campground without using the motorhome. Most any subcompact car should be able to haul an empty trailer at campground speeds without damage to the car or being dangerous to passers-by, even if it would be unsuitable for pulling it down the highway.