I only have room for 1 setup at once, with room for another folded to swap out...
Personally I think that 3 would be a perfect number, with diminishing returns after that.
Massive collections look better, but when I visit friends, we usually focus on only 2-3 titles in any 1 afternoon.
Still, a huge collection allows you to host large groups if that's what you're into.
I do feel that one benefit to having fewer pins is getting to know them better. A game like ACDC is deep enough that it's tough to truly appreciate it unless you spend a lot of time with it.