Which work better 4 ram 2gb or 2 ram 4gb

[Guest]

which work better 4 ram 2gb or 2 ram 4gb (or perhaps 2*2gb+1*4gb) {fbs 1333 , cpu core i72630qm}
is using more channel make faster read?
use same type ram (in size) is important

 

[Leaps-from-Shadows]

2x4GB is a better configuration.