I have a 2014 Grandby with the inside shower. I have used the inside shower about 3 times, when it was really cold and I'd just hiked a lot with a lot of elevation gain, and really needed a shower. Like in Yosemite in November.
I use the outside shower more, as it is a bit less trouble to set up and there is not any moisture inside the camper to deal with. In hindsight, I may have been just as happy making up my own inside shower set up, as poster MINO above has described. But one way or the other, I want to have the ability to shower inside on the days when I need one, it is too cold or too windy to use the outside shower, and I am camped somewhere there is no 'campground shower' available.
I also have the cassette toilet, which is used a hell of a lot more than the inside shower. If I was to delete one option, I'd keep the cassette and delete the inside shower, but make up my own setup to allow an inside shower.
It is a personal decision. Everybody has different needs and preferences. However, my lady friend has no particular issue using the outside shower enclosure. She is fast, and as long as you aren't doing it with a light on inside the tent enclosure at night, there is adequate privacy.