Hi, All the RAM quality is the same, but you pay for the name Apple extra.
If you want a nice update of your mini RAM, kost only arround the 29,00 Euro for example 2X... (always 2 of the same type)
(Trancent) 4GB DDR3 1600 SO-DIMM
Apple uses also speed 1600, with a lower speed 1333 your mini wil also work.
But 1600 is nice!
Online shop in Holland: www.Geheugen.com
Tip: Always when you open your Mac, use thin rubber disposeble handgloves for electric static dammage.
Good luck!