I am an incoming freshman majoring in Computer Science looking for a laptop to use long-term, and I am torn between getting a used 2013 retina Macbook Pro vs getting a 2015 retina MBP from the education store. Getting the 2013 model would save me a ton of money, and as a student, that is definitely great. But since I plan to use this thing long-term, would it be better to bite the bullet and spend big on the 2015 model if it means more longetivity and future-proofing? Also, is the difference in performance huge enough to warrant spending much more for the latest model? Thanks in advance!