I think 6.9"was perfect. I'd like bigger screen but it would be a bit too big to carry around, fit in your pocket or even handbag, and hold it with one hand to take pictures. 6.9", 7"the most would be perfect with proper light and colour balance.
The S24U feels great to work with, I wish it was 1" larger and a bit rounded at the corners, but it's not very significant, I am enjoying it the way it's designed anyway, because because of the great software.