Going based on what I've heard about prior years, April is the best time of year to take the MCAT. A lot of people will be trying to take classes and study for the MCAT simultaneously, so naturally this will cut into their MCAT studying which could potentially increase the curve. (Though I'm basing this on hearsay). Plus you'll have your scores back by the end of May, and will be ready to apply with everything ready in the beginning of June.