If you are currently using Mavericks I would strongly suggest that you stay there. I tried both Yosemite and El Cap. and I was disappointed with both of them. Yosemite (for me) was just awful, the UI was laggy and Safari + Wireless was horrendous. El Cap. was an improvement, but it simply does not compare to the snappy response and feel that I get running Mavericks.......and here I will be staying for the foreseeable future.