I was offered at place at the University of Cardiff. long time ago, that's a great place and is a full research grade uni - member of the Russell Group of Research Universities - that's not that important, except some employers in some subjects have historically preferred Russel Group students.
However I went instead to a tech college in Chelmsford, later university of East Anglia, now a car-park - and I had a great time.
My bro did art at Swansea, he enjoyed his time there, but had to do a different degree later to get a good job.
Aberystwyth is famous, a bit, for being a bit hard to get to! But they are a welcoming uni, if you can find it.
The best suggestion, is not to be so worried about "which is the best" but try and attend an open day (either formal or informal) at both University of Caerdydd and the Swansea University, and see which you prefer, talk to your future professors on your choice of courses, that is really a very very very useful thing to do!