I'll interpret this question to mean that we'd remain "ourselves" in terms of personality, and the choice is between suddenly finding ourselves with the abilities, tools, and alter-ego of either Superman or Batman.
So I'd pick Superman, because aside from the fact of his actual powers, there's the simple fact that if you started out as Superman, there's no reason you couldn't change into Batman later. Superman could be Batman if he wants -- change the costume and you are just Batman with all of Superman's powers, which I think helps negate the loss of things like chemistry and science and stealth because if you can use X-ray vision and see across the galaxy and move at nearly the speed of light and are invincible, I think those other things become ultimately less important.
Example: Batman can use his skill and knowledge to track and defeat the Joker. Superman can fly over Gotham at the speed of light, listen for the Joker's distinct heartbeat and voice, and swoop in at super-speed to grab him and knock him out.
Superman's powers do mean that he relies less on brain than Batman in many crime-fighting regards, but Superman isn't exactly a mental chump. He's extremely smart, has immense science skills and alien technology (if Batman gets money and Wayne Enterprises and his science and tools, Superman has to get his Fortress of Solitude full of alien stuff, yes?), is a top investigative journalist, and with his powers could -- if he/you wanted -- just take a year off to use superpowered study habits to become as proficient in detective skills and martial arts and chemistry etc as Batman, and then fly back in time so it took him no time at all really.
I think that being Superman would give you the chance to have all of those powers, use them to get good at all the stuff Batman can do but even better (because you do it as fast as light and are indestructible), and just become Batman with superpowers, if you wanted.
Honestly, though, even if it was just a case of either being able to fly, see through things, be indestructible, move at superspeed, and have super-strength, those powers alone would be more worth having than being Batman. I'm a huge fan of both Batman AND Superman, but yes, Batman is by far my very favorite character of all time. And of course most guys would love to suddenly have the skills of Batman, so I'm not knocking them, I'm just saying that really compared to having a bunch of actual incredible SUPER-superpowers, there's no contest. Anything I could do as Batman, I could do as Superman, but faster, plus I could do everything Batman can't do as well.
In a real-world situation, as Superman I'd fly around the Earth at a high altitude, using my super-vision to locate every piece of Kryptonite -- it might take a while, but I'm Superman, and I've got time. Then I'd swoop by at super-speed with hot melted lead sludge, and wrap it around the Kryptonite to encase it so I can grab it and fly off with it. Then I'd hurl it into the sun. Give me a week, and almost all the Kryptonite on Earth will be gone. Someone has some hidden in a lead box somewhere? Good thing I regularly use my X-ray vision to scout ahead of me for dangers, and will see any Kryptonite or suspicious lead boxes. But hey, if someone suddenly opens a box to reveal Kryptonite -- I'm Superman! I move at the speed of light, almost! I have heat vision! I can fly! In short, I think that it will be hard for a mortal human to sneak up on me with Kryptonite in a way that prevents me from reacting faster than the speed of thought and thus faster than the time it takes them to begin smiling as the box is opened. I'd melt the box around the Kryptonite (and it's a lead box, which is the only way they snuck up on me with it, so the lead will stop the effects of the Kryptonite), while I simultaneously fly up into the air away from them to avoid even starting to feel the effects.
In short, I'd be a Superman who doesn't keep getting surprised by a middle-aged bald man with the one single substance I know I need to watch out for. So to me, being Superman means being invincible, flying, seeing through things, etc. Which sounds like fun.
But overall, I have to admit that most men probably would respond to the question first by saying "Batman," and then would come back days later, after realizing they just gave up being bulletproof and X-ray vision, and say "I'd like to amend my answer." And seriously, I'm one of the biggest Batman fans in the history of ever.
Batman by a significant margin.
Admittedly, my research is not impeccable and is largely google based. This is the closest survey I could find on the question: http://moviesmusicmayhem.
As trite as the analysis in that survey is, I think it hits some truth.
Superman is Kind of Lame
What exactly has Superman done for us?
With the powers and technology at his disposal, Superman could change the world for the better, invent fusion (people forget he's supposed to be super smart as well), fix global warming, etc. But he never does. He built a 'Fortress of Solitude' instead.
He's a lonely guy just trying to fit in.
Remember that Clark Kent is Superman's mask, not the other way around. He's an alien stranded on earth. His real name is Kal El. He doesn't really fit in.
That's even worse when you consider that from an alien perspective, the bumbling Clark Kent is what Superman thinks of us. He picked the disguise to blend in, so that's what he thinks is a normal human. Somewhat ridiculous. Uncoordinated. Lame.
Superman seems to looks down at us on some level.
He's the pinacle of moral superiority. He doesn't use his powers to fix the world because he thinks we should have the choice to do it ourselves. He's kind of a jerk that way.
Even if he might be right.
What's worse is that he has no business looking down on us. How did he get his powers? Born with them. Advanced alien technology? Given to him.
What has he accomplished on his own, with his own hard won skills? Well...I think he won a Pulitzer at some point in the series. Kudos dude. Better than I could do, but seriously? With all those powers and gifts, that's what you came up with?
We don't really get him. Why does he do that stuff? Because his mommy raised him on apple pie? Why not just take over the world? Or at least peak under Lois's dress with x-ray vision?
He's just a fantasy, and at some level we recognize that. Given the choice of becoming him or Batman, we'll pick the choice which is perhaps understandable and real.
Batman is Us.
Batman, on the other hand, is real. Not realistic, but he's a very real character.
He's been driven somewhat mad by motivations we can understand. Who wouldn't want to beat the crap out of bad guys when you've seen your parents killed in front of you?
He's dark. He's conflicted.
Remember that Bruce Wayne is Batman's mask. Bruce Wayne is a complete sham. Batman is the true self.
He earned his skills and attributes. Sure, he's rich. He didn't earn that. But he took all the rage inside him and became something greater through force of will. He wasn't just born that way like Superman.
We admire that.
Every time someone pushes us around, steals our girl, or cuts in line at espresso bar, we want to be Batman. Not some goody goody mama's boy. We want to kick ass.
He is one man fighting against the world with nothing but his will to sustain him.
But still, he never crosses the line. He never ever kills. Despite all that rage, he keeps his $h!t together. He knows that sometimes you have to break the rules, but he never breaks his own rules.
He is ... noble.
No matter the odds, he comes out on top ... and then lets you cry uncle and sleep it off in Arkham.
Batman vs. Superman
Whenever it comes down to a fight between Batman and Superman, who wins? Batman.
It's always out with the kryptonite and kick Superman's ass.
This seems to be a fairly typical survey:
Even when Superman thinks he's gotten rid of all the kryptonite, Batman synthesizes another batch because he knows one day Superman might have to be taken down.
In a "realistic" fight, sure ... Superman would win. But we don't let him. The writers of these books know what we know in our imaginations: we don't want him to win.
We want a human to win. We want to win, and Batman represents us, flaws and all.
What powers would you want, Superman's or Batman's?
Obviously Superman's. Batman has no superpowers. It's the obvious rational choice.
But who do you want to be?
It's not a rational choice. It's an emotive one.
By Maya M. Wagoner, in consultation with Ben Cody
Boys want to be Batman. Men want to be Superman.
This is kind of a glib answer, but really, as far as superhero power fantasies go, Superman represents a much more mature kind of idealism than Batman. Consider: Superman is a working-class superhero, "more powerful than a locomotive." He has a job, he has a wife, he has a boss. He grew up in America's heartland, working on a farm in a small town. In contrast, Batman grew up with all the money he could ever ask for, and no parents nor authority figures of any kind. He's like James Bond without M; he gets the cool car and the gadgets and babes galore, only he's not accountable to anyone.
Furthermore, their approach to the cape and tights are totally different. Batman's all about striking terror and being feared, while Superman intentionally dresses in the most neutering, harmless, visible costume he can. For Superman, it's not only about downplaying his tremendous capacity to destroy, it's also so that people know him when they see him, and they know when they see him that everything will be okay.
Which brings us to a final point: the focus of their methods is very different. Batman is out for his personal satisfaction. This is undeniable. If he was really concerned about crime, he'd spend all his money on social reform, not private jets and custom cars. Instead, he spends his nights personally handing out beatings to the mentally ill and the economically disadvantaged. Protecting the people of Gotham is secondary at best; primarily, and by his own admission, Batman "is vengeance." The conflict of most Batman stories is "can Batman beat the bad guy?" And of course, he always does.
Similarly, Superman always wins against the villain. But for Superman, victory is a foregone conclusion; thus, the real question tends to be more along the lines of "can he beat the bad guy AND save Lois / Jimmy / the Earth?" The conflict arises from the responsibility Superman assumes, not from his capacity for violence. This is why the Superman myth speaks to the best qualities of a man, and the Batman story to a far more adolescent, selfish fantasy.
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