imgur.com/ueRN4F6
here is the brightness distribution for the aero 15x 4k panel. Panel is model is AUO_B156ZAN03_1. This was taken with Xrite's i1 profiler software. Bottom left corner (lowest brightness at 377 nits) was also the only place where there was noticeable back light bleed.
Some things i would like to add. Ghosting is similar to Dell XPS 15 9570's 4k sharp panel, which leads me to believe the response time of the AUO panels is 60-ish ms. The matte layer on the panel makes the gigabyte's 4k panel seem brighter than that dell's 4k panel, in bright condition, even though the xps 15 i have has an anti glare coating that reduces the intensity of light reflected, and the dell panel has a brightness of 450nits. the trade off is though, the matte coating makes pictures seem grainy and text not as sharp, although the difference isn't that prominent.
another thing to note, gigabyte's 4k display had a slight hew shift along the edges (VERY slight, you won't notice unless you really focus on it). the dell's 4k display doesn't have that.
Forgot to add battery life. Both dell and gigabyte with 4k panels get same battery life. Which means, fully updated as of September 20 with drivers, bios, and Windows 10, ~5 hours of 1080 60p or 4.5 for 4k 60p youtube on firefox, and ~8 hours of excel/word + playing some music. i know its not much of a comparison to notebookcheck's standardized tests, but its the best i can do since i no longer have the machine. Also, i feel like some recent updates have reduced battery life for both machines.