I would say that the answer depends on what kind of pvp you enjoy. Do you like strictly 1v1? Are you a mass pk player? Looking for small or solo pk?Also, after answering that first question; are you looking to be a damage dealer or a support player? (both of those classes are more on the side of combative support in large pk)
for 1v1 and damage dealer
If you strictly wish to 1v1, you might want to try a BM. I will advise you though that BM is not even remotely easy to learn when you start it. Barb is a little simpler when it comes to skills, but you must build it correctly in order to be effective (i.e. don't stat vit). They are both very effective in 1v1. I'd like to give more advice than that, but I can't say for sure which one you'd enjoy more. They are both very nice 1v1 classes.