You can have my composting toilet when you pry it from my cold, dead....uh....nevermind.
Zero complaints about having a composter. My original homemade one had some less-than-elegant design features, but worked fine. The newer store-bought one is great so far. My reason for a composting toilet? It's waterless. Water is heavy and takes up space, and it has to be stored, pressurized, delivered, then stored again after being peed/pooped into, then dumped somewhere. Once the alternatives are considered, using water as a medium for transporting and storing human waste is not really necessary. With a waterless model, there is a lot less plumbing and mass of stuff to deal with. A powered vent to the roofline will take care of smells. And the resulting smell is no where near as funky as a blackwater tank where #1 and #2 stew together to make a "latrine" odor.
If a person is always going to be on full-hookups, it's a moot point. Flush away! If you're going to be boondocking, or staying where there is only a dump station some distance from your rig, I think a waterless toilet is well worth consideration.
IMO, YMMV, etc