Is it an OS version issue? I haven't updated my OSX in ages (mainly because I don't like the direction its going, and updating seems to be guaranteed to fuck up

Is it an OS version issue? I haven't updated my OSX in ages (mainly because I don't like the direction its going, and updating seems to be guaranteed to fuck up my Logic Audio install like it does every damn time), and iTerm runs amazingly smoothly on it as is. I feel no lag with it and I spend a lot of time on the command line (Lisp programmer on vim ... go figure...), so I'm wondering if these numbers even matter after a certain point, or if later OSX versions are doing something crappier than the usual.