The good thing about a propane generator is that it doesn't get clogged with varnish, although it is a good idea to run it to keep the windings clean.
Downsides is that propane tends to be harder to find than gasoline, and since propane has less energy than gasoline, it gets used up fairly quickly.
As for cassette toilets, they might work in Europe, but they are somewhat hard to dump into a normal dump station hole because they weigh 60-70 pounds. Because they do splash, CG owners hate people emptying them in the bathrooms. I prefer the ease of a black tank, although both are far better than recirculating toilets which require draining, then pre-charging of the system again with fresh chemicals and water.