In our case it's not a preference, is the sexy fun of it. Neither Mary or I like to drink lots, don't mind filling mouth, but mostly let it run out again. Maigh has a good try of chugging it down, but she can't keep up either, maybe a quarter will foam and froth back out.
If there was a choice, I think the potty would win most times, we don't have a dominating type of relationship, but when we are 'in a mood' anything can happen, and usually does.