this question comes up fairly often.
there are as many answers as there are members of the forum.
we use our on-board shower and the campground showers about fifty fifty.
a camp shower is usually bigger and has lots of hot water, which makes for a relaxing time instead of in and out Navy style.
or we're planning on staying in the campground for a week and don't want to have to make a run to the dump station for more water and dumping the tanks before moving on.
or we have our granddaughter with us and she likes loooonggg showers every day.