I've been to both Cluj and Plovdiv, Cluj was by far the most interesting city for me, Plovdiv was rather sleepy. A lot of people remark that Cluj is a university city which is correct, but in particular sport hence there's a lot of strapping lads there, competition levels are high.
I wouldn't live in either city, out of those mentioned above I would choose Wroclaw
I wouldn't live in either city, out of those mentioned above I would choose Wroclaw