As pointed out in this thread by someone who used the books and took the MCAT, old BR books are fine. Many people have been getting great scores using a mixture of old and new BR books. I have posted my opinion about this a few times and it repeatedly gets reaffirmed (thank you Miami_postbac). I also point out that Organic Book II (the current one) has a large amount of biochemistry and if you only get one new book, that is the one to get. That book is where we added a significant amount of structural biochemistry and biological reactivity. It also has shortcuts for sugars, isoelectric point, and so on.
However, I do want to add that at this point you shouldn't have to ask the question about new books versus old books. If you are looking to save money buying used books, there are now plenty of the 2016 books floating around. I know we were late to market (the last of our new books came out at the start of Summer 2016), but that was to make sure we modeled it after the MCAT and not a practice exam written in 2013 and released in early 2014. Our newest books are the best materials for the MCAT period, with our older ones running second. If you can get older books used for $200 versus current used ones for $300, why not spend the extra money? They'll have higher resale value and the amount you are saving is what it costs to apply to a couple medical schools. Again, old books are fine and if you have them already, you'll be fine. But the new ones are better, and if you are shopping for used books (or new), choose the current ones.
One thing I would ask/suggest is that if you are shopping for used BR books (or selling them), do it through SDN classifieds. It is a great community and we suggest to our students to sell their books there, as opposed to other places. Amazon is NOT an official seller, and the books there are often VERY old and overpriced. Ebay is also a pool of outdated books and Craigslist is often a crime waiting to happen.