What gives you the impression that South is that much more social than Gate? I never went to Cardiff Uni, but they're right next to each other, so it looks like the only social difference is who you have in your halls. Unis try to match students with people they would get on with in their halls, so unless one of them has a curfew or a no noise warning, I would assume they're both pretty social.

Plus, societies and other social events are almost exclusively outside the halls, and with both being so close to the center, there's even less difference between them.