Benefit of the lower 1/3 , your head is not bent forward , and you can run the stock shorter .
For the absolute , your irons and your red dot line up , if one is zeroed then the other can be easier to dial in [ I've never had issue with a FSB being a problem co witnessed with a red dot ] .
Something else to think about , the sights on a AR are already high over the bore axis , with the lower 1/3 you're raising them , albeit marginally , higher above the bore .
YMMV.