I have a 2012 Mac Mini and a 2013 MBA. I am currently running El Cap on my MBA but need to upgrade the OS on my Mini. I would like to keep them on the same version of macOS and will likely run it for the next year. I have found only one thread which indicated a loss of battery life for 2013 MBAs running Sierra, so I am wondering if anyone has any further input on performance and battery life for older MBAs running Sierra? Is it better for performance (obviously not security) to stick with El Cap or does Sierra offer comparable performance?