I don't know if my comment would be relevant given the date on the post, but on the off chance it might, I'll comment. Just started first year, and so far I'm liking Cardiff. In terms of the city, It's basic things like a good measure of shops being really close and a short walk or bike ride, not all too expensive to live in, friendly people, good cinemas among other things. In terms of accommodation, I don't know all too much about Uni halls, but Cardiff has more than enough residences that are private and uni owned that suit nearly all preferences, respectively. I personally don't like the uni halls out of personal preference and opinion and opted for private accommodation. I don't know all too much about Liberty Living, The CRM owned residences, The Neighbourhood among a few others, but the one I'm staying at is targeted at the Asian student population more than anything, which can be concerning in terms of making friends cause it does seem that they're In their own bubble at times compared to all the other tenants, but that could be more of a personal thing on my part and you could easily make relationships through clubs and societies. It's not a bad thing, I quite like it here, everyones friendly and welcoming, but probably do some background research or contact these places if it's a point of concern for you.
I'm not one for going out, but I hear the Nightlife isn't all that bad, if at all. I heard Jason Derulo was playing a few weeks ago in Cardiff and on top of that most people from the Uni really like to hang out at Live Lounge and other clubs nearly everyday of the week, or at least once. I hear that the Talybont halls are the most social dorms.