Getting back to the original post, I have experience with 3 types of toilets typically used in vehicles. I have an RV with a traditional black tank, a porta potty in an outbuilding, and a bucket toilet in my van. They each have their pros and cons. Which one is best depends on the use case. My van is my daily driver, I've also done dozens of road trips, including coast to coast 2x. I almost never use public bathrooms.
My blank tank, at 50 gallons, is never the limiting factor. Still, its inconvenient because it has to be driven to a designated place to dump. But since I have to refill the fresh water tank anyway, its unavoidable. The dumping process is more complicated than the other toilet types, but there's no smell when dumping or from the toilet, unless something is wrong. The toilet needs to be cleaned just like the toilet in a house. The black tank needs occasional attention also. Males can remain standing to pee.
The porta potty looks and sits like a regular toilet but it is lightweight and can be moved anywhere at will. It needs to be cleaned the most frequently compared to the other toilet types. The tank is tiny, how frequently it needs to dumped is dependent on how many people are using it and how often. Doesn't matter if its solid or liquid deposits. It is guaranteed to smell very bad when it is dumped. The tank needs to be cleaned after every dump. I do this process outside, using a garden hose and soap. Cleaning takes significantly longer than the other toilets. Males must sit to pee (the bowl is not deep enough) to avoid splash back. Lastly, these toilets are shorter than regular toilet height, so taller people will be in a squatting position when sitting.
My bucket toilet is the kind of composting toilet you see homesteaders on YouTube build. It is an ottoman made of wood. Under the lid is a regular toilet seat. In the compartment below it, a 5 gal bucket lined with a plastic bag containing pine pellets. These expand as pee is added it, no cover material needed. Males can remain standing to pee. In around town use, I've gone 3 weeks without emptying it. On road trips its my only toilet, I empty it every 4-5 days. Unless I poop in it, in which case its time in my vehicle is measured in hours. The only odor is the smell of pine pellets. The toilet also doubles as a trash can for coffee grinds, food remnants, stuff I don't want to put in the vehicle trash bag. There is no cleanup other than occasionally wiping the toilet seat with a Lysol tissue. The bucket does not typically need to be cleaned, but even in the worst case (ie. bag leak) it takes less than 30 seconds to pour in a some Clorox and wipe it out. I would not want any other type of toilet in my van. I don't want to have to search for dump sites like I do with the RV. I don't want to search for toilets to dump a porta potty. With bucket toilet, I tie-up the bag and dump it at the most convenient gas station, big box store, or rest area.
