When Samsung first released the GS5, we thought the 5.1" FHD Super AMOLED display is pretty similar to the 4.99" FHD one used in the GS4. But DisplayMate found out that this is a much superior display in many aspects, one of them being that it is 27% more efficient.
 GS5 subpixels |  GS4 subpixels |
Samsung told DisplayMate that the improvement mostly came from more efficient OLED materials. They also incorporated new display electronics and optics and that helped as well. But now Chipworks posted a teardown of the GS5, and they published a macro image of the display's sub pixels. It turns out that it's a different architecture than the GS4, and this may explains some of the performance boost, too.