I think BCS will make the pivot to more tragedrama in the final season only because I think the resolution of the non-BB characters (ie Kim) will be pretty tragic. (Not predicting she dies, but there's probably a good reason we don't ever see/her about her in BB).
To answer the main question: It is hard to say one is better than the other as they are quite different. It's also hard to judge since one is a completed series while the other still has one season to go. BB had such a great finale/resolution that if BCS somehow doesn't stick the landing (which I don't think will happen, Vince is an amazing storyteller) you will probably hear that BB is superior.