I enjoy going to all three.
Pubs are good for meet-ups getting casually drunk with a lot of natter, clubs are great for getting trashed mucking about on the dancefloor and bars are inbetween.
I havnt really been to many bars, Id probably prefer them most if I did but between pubs and clubs, clubs are most fun.
Funny I did a pubs vs. clubs poll before I went uni and said pubs and that I was anxious to go clubbing.. how times change