What's it like? Awesome dudes!!
Union - Has everything, including a few bars and a club (or clubs??), on 4 storeys
City - 3 Shopping centres, a few hundred more shops, the same amount of bars/clubs (the best?? judge for yourself)
Going out - cheap student nights all week, good vibe
Food/shopping - yes, plenty and good
Accomodation - HALLS, not HOUSE for first year, ALWAYS (because it's much better living with people you've developed a bond with). If you've got a place in Cardiff, you've pretty much got a place in halls
A visit is strongly recommended, just to see how good it is for yourself first
Cathays, the main student area is worth a look too, just to familiarise yourself with the place