Greetings, We have several MacBook pro's (2011 thru 2013's) at the office and once a year we do a clean install. We recently installed the latest Mac OS Sierra on a 2011 and felt the speediness of it decreased. My initial thought is well they meet the system requirements new OS's take advantage of newer hardware and it's seems obvious older ones will not keep up as well. Anybody have any thoughts on this? I was thinking pick an older OS that still has all the features I need and install those on the older machines for best performance?