Amesterdam would be pretty cool. I can only imagine how much trouble I could get into. Wait, EVERYTHING is legal there. Never mind.
Bruge (which is actually pronounced Broo-Hay, not brooosh, if you want to sound local) is pretty nice too, but it isn't going to provide the adult oriented activities. Pretty dam$ good chocolate and Belgian beer though.
But, in my current sitch, I would vote for Amsterdam.