I don’t see how he stays dark in one but not the other. The suit? The lighting lol?
They emphasized the fact that he was the great hope. He was practically All Might in the Snydercut where the villains started ramping up because they knew the symbol of peace was gone. That whole ending (if you dismiss a dream...) with Superman had a more upbeat Superman who was confident in his abilities and enjoying the fact that he’s back. Not that the theoretical cut didn’t do this but it definitely didn’t highlight how the loss of Superman effected characters like Lois or emphasized his importance of being on Earth. To scare alien invaders like Steppenwolf away.