I work within the Harvard medical system here in Cambridge and thankfully multiple people have confirmed there is absolutely no advantage given to MCAT 2015 testers and that MCAT is good for 3 years regardless. However, I would argue that a "standardized" test's value lies in it being standardized and if there are two completely different versions, how will adcoms be able to make an objective decision, especially those that weigh these tests as very important.