As I stated above though, someone not taking a gap year must complete the MCAT ideally by early may after junior year (since ideally you should submit AMCAS the day it opens with scores in hand), at the latest by the end of june requiring MCAT prep concurrent with school and working on your AMCAS app. A person taking a gap year has the luxury of taking it at the end of the summer after junior year with MCAT prep occurring outside of school or working on AMCAS. My commitments during the school year (D1 athlete, fraternity stuff, school in general) far exceeded a full time job so studying for the MCAT and working on AMCAS on top of all of that would have been a hindrance. The gap year allowed me to do MCAT prep on top of just a full time job, and then I could work on AMCAS all during senior year (although I actually I took 1 month off between graduating and my job and just did it all then, submitting my AMCAS on an acceptable, but not ideal late June day).
So, depending on your school schedule, that gap year can make a huge difference on your MCAT based on the amount of time you can devote to it.