2015 MacBook Pro: Photoshop Performance
Authorized Apple dealer B&H Photo loaned MPG the Apple 15.4" MacBook Pro Retina (Mid 2015), 2.8GHz / Radeon R9 M370X / 16GB / 1TB, the configuration MPG recommends for power users, photographers, videographers, etc. Save money on AppleCare too.
When memory is adequate and I/O is not involved, the 2015 MacBook Pro Retina and the late 2013 MacBook Pro Retina are all but identical in performance when CPU clock speed is accounted for:
Photoshop Speed: diglloydSpeed1 and diglloydMedium Photoshop Benchmarks
But should memory run even a little low (causing swapping to disk), the blazingly fast SSD in the 2015 MBPR then trounces the older model, that older model having a much slower SSD.