A regular disk always trys in the background to spin,specially to see if its needed,while a ssd works always then whrn yo u really need it.SSD protects ur battery life not necessarly the durance of a useing cycle,but ivy bridge does!
Intel claims Ivy Bridge uses 20% less power. The retina screen in the iPad 3 increased power draw for the screen alone by 300%. A retina screen would still hammer battery life in a 15" MBP without increased battery size and weight.