If it were up to me, I'd pick Cardiff simply because I love the campus and city. Perhaps future wise, choosing Cardiff or Liverpool could be more beneficial as they are both Russell Groups. Liverpool, I heard, hasn't got the best SU but I can't imagine the night life being too bad as it's a huge, vibrant city. You're right about Leicester, the town doesn't compare to Cardiff or Liverpool.
But yes, in my opinion, go for Cardiff. Good degree, great city, beautiful country; I'm sure you'd enjoy it.