Hey there - I'm Mostafa, a current student and ambassador at Aberystwyth University.
I wouldn't say there's one accommodation that is "more social" than the other. There are events hosted throughout the year by the Res. Life team who plan everything from painting sessions to game nights and movie nights which are free and open to all students living in university accommodation.
There are also lounges such as the Rosser lounge, PJM Lounge, Fferm Hub and Y Ffald in Fferm Penglais which are again open to students living in accommodation and are social spaces where people can hang out.
During the beginning of the year, there'll be a flat mate meeting organized by the Res. Life team which gives you the opportunity to meet and get to know your new flat mates.
Hope this helps!