What I would suggest is looking at the apps you need to run and see if there are issues with any of these newer OS versions. To be clear here: I have a late-2013 MPB, so performance will be different. And unlike running newer iOS versions on old hardware, I haven't seen a degradation in performance with newer OSs. I'd probably still be at 10.6.8 if I could, but I've been fine running what I need to run up to Sierra (10.12). I haven't seen a compelling feature in years. To be honest, the only reason I upgrade my Mac is because I need to to run a certain application (usually something from Apple).
