If you are more concerned by ethics than by bigger bang for the buck, do like me:get a www.fairphone.com
It is a very good phone and completely open (i.e. rooted)
Plus they will most probably support installing other OS'es like FireFoxOS and Ubuntu Touch.
Not many phone producers go that far.
Eh. I've seen that before, and it really doesn't seem convincing to me. They claim to put 'social values' first, and then make a phone with a MediaTek chip produced in a random Chinese cheap labour factory. And I'm guessing that's the case for some of the other components as well.
I'm glad that they're leading the way by making sure the phone itself is made in good working conditions, but that doesn't mean much unless they closely monitor where the components come from.