What is the difference between a restroom trailer and a portable toilet?
All of them have sinks, real flushing toilets, mirrored vanities with lights, and are climate controlled. Restroom trailers are a major upgrade in comfort compared to portable toilets.
In contrast, portable toilets are made for one occupant at a time. Most portable toilets do not flush although they can be modified to flush and sinks can be installed internally. They are not climate controlled and few come with mirrored vanities. Solar-powered LED lights can be installed in portable toilets.