OS X 10.11 (El Capitan) soll auf (älteren) Geräten mit HDD etwas performanter sein als OS X 10.10 (Yosemite) …
http://www.iskysoft.com/article/mac-os-x-el-capitan-vs-yosemite.html
http://9to5mac.com/2015/09/29/os-x-el-capitan-review-roundup/
http://www.gottabemobile.com/2015/10/04/os-x-el-capitan-on-older-mac/
http://thenextweb.com/apple/2015/09/29/os-x-el-capitan-review-the-rock-solid-update-yosemite-and-ios-needs/
http://www.macworld.co.uk/review/mac-software/os-x-el-capitan-vs-yosemite-3619741/