I have been looking at a number of trailers and have been trying to be flexible so as to give myself more choices for trailer purchase. I know that seems odd as most people try and narrow their choice...
In general 'wet baths' only exist where there isn't enough space for a separate shower stall.
Thus by definition, they are tiny.
It's largely a compromise you have to make about how much space you want to give up for the very limited amount of time you use the toilet and/or shower.
If you are a large person, you will likely never be happy with a wet bath due t the size.