OS X Mavericks vs Yosemite Performance I am using a 2013 MacBook Air and considering to upgrade from 10.9 to 10.10. Is there a performance gain after the upgrade? Is Yosemite faster than Mavericks, say, regarding UI responsiveness?
Quick answer: NO. Yosemite isn't faster than Mavericks.
I don't say that the performance is worse. The oldest is the computer most noticeable is the difference. But, on a 2013 computer, it should be the same, or nearly the same, on both machines. Anyway, there are things you can do to improve it (How to Improve OS X Yosemite Performance).
What I noticed, is that is quite more efficiently on batteries.