I prefer Batman. There are many reasons for that, but they all boil down to the following main points.
1) Batman stories often put a much larger emphasis on the Batman's intelligence than Superman stories do on Superman's.
With Batman, his greatest strength after his indomitable will is his mind. More specifically his detective/tactical skills and clever ways through which he gets out of situations, both in Gotham and in JL adventures. It's not that Superman is an idiot, but a lot of writers seem to put more emphasis on his brawn than brains even when the brains are there. Heck, a huge theme in the Superman/Lex dynamic is the human mind being capable of keeping up with the physical powers of a god. The intelligence aspect in Batman is far better represented and emphasized IMO, and that's why I lean towards Batman more. Honestly, I think that's the #1 reason DC has such a hard time compared to Marvel. For every physically overpowered character, Marvel has like 2 or 3 mentally overpowered characters. We live in a society where a person's mind is considered first-and-foremost as their greatest strength. Being a great detective or great scientist is the new "he's faster than a speeding bullet".
2) Batman is an extraordinary character in a ordinary world; Superman is an extraordinary character in an extraordinary world.
People often say they like Batman because he's realistic. I don't think he is, but I do think he fights the most realistic causes out of all the heroes, and it's all due to Gotham City. I always said that Gotham has become the world, or at least the way we see the world. If you think about it, all the issues we hear people complain about on a daily basis - crime, police brutality, corruption within the justice system, corruptions within corporations and the upper class, urban decay, environmental issues, terrorism - ALL of those problem exist in Gotham. Even in the case of a less realistic and more stylized portrayal of the city, those fundamental issues are still there. It's arguably the best location in all of comics for social commentary, and why Batman lends himself to social commentary so much. Whereas Superman's world (mainly presented through Metropolis) is almost-by-nature less realistic. There's still a lot of social commentary there (i.e. Luthor), but things like alien invasions aren't as fascinating to me in comparison.
3) Of all the superheroes, I think Batman is the most balanced one. He has found the perfect balance between lightness and darkness.
People often say the opposite of Superman is Batman. I don't agree with that. The polar opposite would be the Punisher IMO, whereas Batman is right in between. Batman is the hero who learned to strike fear and terror in the hearts of criminals the same way Punisher does while still keeping the compassion and heart of Superman intact. That's the thing I think a lot of people overlook regarding Batman - including writers - is that despite all that darkness on the exterior, he really has a heart. To quote Amanda Waller, "there is no one who cares as much for his fellow man as Bruce Wayne". When Superman makes his speeches to the superhero community over the importance of not taking a life, I always feel Batman is the one who understands what he means the most. That's why they're such good friends (yes, they're friends, despite what the e-wars would have you believe). They have different methods, but share the exact same morals and values. Superman also has that heart and compassion there, but he doesn't strike fear in people the same way Batman does (and I don't expect him to since he shouldn't be dark; don't jump at me Superman fans).
Where are the "both" and "neither" options?
