EK = Bare bones Ochem. If you don't need much of a review this is for you.
BR = Comprehensive Ochem review and tons of passages for review. If you are weak or shaky in Ochem this is for you.
I had both, but ended up using EK for 90% of my Ochem, just because I ran out of time and I used to tutor Ochem, so I felt fairly comfortable with it. But if I have to retake (I'll know soon enough), then I will use BR to get the comprehensive review and the passages.
I will also note that in my experience with Ochem passages (All the AAMC's, Kaplan 1-4 and the real deal) you don't really need the passage. It's good to skim, but the answers for the questions must come from your understanding of molecular interactions. So, if you're weak on how molecules interact AND why, go with BR, because the passages aren't going to help you answer those questions.