Lots of choices and [in my opinion] not a whole lot of reasons to choose one over the other. They all work reasonably well if properly installed and set up, but you may have a preference as to hook-ups, permanent mount vs portable, etc.
And if you have a non-air brake motorhome, it probably makes more sense to go with a unit that does not require a coach air supply. But even that is not clear call, since most offer an auxiliary compressor to mount in a non-air coach.
If you have a coach with air brakes, the Brakemaster system is simple and easy to install and relatively inexpensive if purchased online. If not, a Brake Buddy is a popular choice. Unified Tow Brake and SMI Air Force One and M&G are some other popular choices.