The one thing i always hate in these arguments are the “But if this was a REAL fight,” which is silly since you’re discussing fictional characters. So you actually have to place the fight on the character terms. Batman wins, not because he’s better prepared, but because his character is fundamentally presupposed to win. His character is that he has to face impossible obstacles constantly:
1. fight crime in a perpetually corrupt city, which as a function of story telling, literally never gets better. So 20 years in, or 40 years in, Batman’s job has not made anything better. But, he can’t stop. He’s pretty much sisyphus in spandex.
2. he also must combat epic-level dangers, and be able to hold his own and be a leader to super powered characters. And since he’s right next to very powerful characters, he can’t be shown as weak, so he’s developed this meta-power of always being prepared.
Since his existence is one of perpetual struggle – victory – struggle, if he lost, it’d undo his character completely.
But Superman is almost the opposite. He’s not a human cursed with a literary hell on earth, and remaining just sane enough to call himself human, he’s an alien who’s godlike, masquerading as a human. So, he must constantly be humbled, defeated, and rise again. Which is messianic in it’s nature, which is what the character represents. So when Superman confronts Batman, he loses, but loses until he realises he shouldnt be fighting Batman anyway. Pitted against each other, they must fulfill their character arcs, so Batman wins, continues in hell, Superman loses and returns to heaven.
Its perfectly reflected in their cities, and enemies. Batman lurks in the dark wet Gotham fighting demonic villains (twoface, joker, killer croc) whereas Superman flies above the skies of sunny metropolis fighting Lex Luthor (A god among men) Darkseid (a literal New God) and Mxyplyzyk (A 5th dimensional God).
So Batman wins, cause he’s written to. But his life sucks in the long run.
Superman loses, but he gains in humanity.