Have a combined loo/shower. Ours has a swing wall so loo etc remains dry. Yes, you walk on shower floor when use washbasin or loo, but it is not like a separate shower tray, the floor is the shower tray. We have a 6.4m PVC so the whole room isnt large and its not easy to dry yourself without stepping out at some point - maybe to get to toiletries that are behind the swing wall. As Brian said, all vans are a compromise, look at lots to see the various layouts. Our first van was after having a 2 berth caravan with a fantastic bathroom/dressing room but just not possible in a small motorhome. We do use our shower and loo, all the time, in preference to site facilities and when on CLs with no such facilities.
I understand the layout Colin talks about - we saw it when looking for our current van. Decided it wouldnt do for us because it didnt allow easy access to bed area and kitchen whilst one person was in the shower, but horses for courses.
Priorities are crucial. You dont spend long in the loo/shower. In our view other aspects are more important, like overall size of van, fixed beds, kitchen big enough to cook meals with sufficient work surface.