DC is inherently a little darker and a little more serious than Marvel, the current trend is that Marvel (in the comics too) makes fun of itself, in an I'm too cool to take myself seriously way is cheesy and straight up detrimental for some characters, "lmao u wearing a cape dude", they make a joke out of themselves and people eat it up (not even kidding), ask darthkostis, DC still takes itself seriously which is how it should be with superheroes, at least with most of the A-listers.
I'm gonna have to dissagree on that. Recently, I've been feeling fed up with Marvel. Constant relaunches, Gwenpool and Spider-Gwen, Squirell Girl, all bloody **** that made my blood boil. So, I went back and started reading some older stuff from both companies to come to a conclusion. My verdict? Despite the recent trends, Marvel was and is much darker than DC.
Let's take death for example. DC's most famous is Superman's, which took place in 1992. There, Kal, valiantly sacrifices his life and goes out like a hero, protecting the world. It's a good tale. The noble hero goes out in a blaze of glory and the whole world cries out in sadness. Of course, being Superman, he came back a while later. DC capitalized on his absence and so and so and so. Twas a good tale.
Now let's look at Marvel's most famous death, Mar-Vell's, which occured in 1982, a whooping 10 years before Superman's. There, Mar-Vell dies not during a physical battle, but out of losing the fight with cancer. The whole story centers around him at first trying to find a cure for his disease (not even knowing what it is at first) and later coming to terms with it. In the end, he succumbs to his illness, suroundedby his friends in a modest bed. No grand fight, no spectacle, the man just... dies. Before he crosses the veil, he shares a very touching scene with Thanos, his mortal enemy. There, he accepts death and walks towards the light alongside his rival. That's probably a dream sequence, and it symbolizes the fact that he's letting go and accepting the inevitable. Honestly, it's one of my favourite pages ever:
To this day, Captain Mar-Vell has not come back. 34 years later, and he's still in the grave. Now, you can argue that DC has had other, more high profile deaths such as Barry Allen's. Well, thing is, this one special because it's not a classic death. It's not about overcoming the odds and emerging victorious, it's about accepting defeat. It's about life itself. That sometimes, no matter how strong, or valiant or noble you are, you can go out like the average joe. Just by your cells multiplying out of control.
Apart from that, most Iron Man comics deal with morality and the concept of war. Why is Stark above the rest? Why does he get to have such a brilliant weapon while pretending to be a peace-keeping agent? You can see that, more often than not, Stark's happy-go-lucky self is a facade. Look no further than Fraction's brilliant run to see such examples. Personally, Fraction's Iron Man might be my favourite run ever. His rise and fall, the character arc throughout it, it's deeply moving and powerful stuff.
In another corner, Moon Knight, at least the first vol, deals with spirituality. But not in an "my aura and my inner self are aligned" way, but in a realistic and down to earth manner. He's a deeply violent man who's trying to find redemption by being the exact same person. He hasn't, for the most part, changed. He hasn't stopped being bloodthirsty. He's still that same merc who gunned down innocents, but because he despises himself, he indulges in a fantasy that can offer him salvation. The Stained Glass Scarlet issues, about a nun who murdered her own son because he was a mob boss are usually the best examples of that.
The X-Men are the best allegory for opression and minorities. "God loves, Man kills" is a classic, and it reads more like a "lost" Image title than a superhero comic. The good stuff can get lost in the endless stories of mutants versus robots, but at its core, the Mutants still stand for the fight against prejudice. Morisson's New X-Men, albeit crazy, portrayed both the beautiful and ugly sides of them. Accepting who you are, versus becoming the very thing you fight against through systematic opression.
I don't think I need to mention Daredevil or Punisher. Both those characters deal with the reality of society and "the streets" much better than anything else. There's no sugarcoating in there, events are protrayed exactly as they are. "The Slavers" is an especially chilling Punisher story, as it captures the human traffic phenomenon perfectly.
I could go on and on and on, but, my point is, Marvel's characters are faulty. They're not perfect or great. Whereas DC deals with the gold standard, Marvel stoops down and deals with the rejects. It's no coincidence that whenever Marvel tries to copy DC characters they never work. Quasar and Green Lantern, Sentry and Superman, etc, etc. They're at their best when they're dealing with the psychos, the monsters and the pricks. Nighthawk is rubbish. But Supreme Power Nighthawk? The man whose parents were the victims of a hate crime who grew up and became just as racist as his "enemies"? Now that's interesting.
I won't pretend that DC doesn't have good stories. Longbow Hunters and Green Lantern/Green Arrow tackled racism and such issues, but they were too on the nose. Hal was reduced to an unrecognizable character in order to play the conservative to Ollie's liberal. The issues they stumbled across were a bit too contrived and not really realistic. The "blue skins vs black skins" line I find rather cringy. Nevertheless, they have great stories, they do. It's just that, for the most part, they're well-written super-hero stories, whereas Marvel's, if you change the main characters, could very well make for great dramas.
And that's the fundemental difference between the two. DC is portraying the "endgame", but through the lenses of pessimism, in order to make the heroes triumph over injustice no matter the cost. It's mean to show that, even if things look bleak and miserable, the good guys will always win. Superman will come back. The sun will rise. Batman, for all of his grumpiness, will let his guard down when he has to. Marvel portrays a realistic and cold world through happy-go-lucky glasses. That's meant to showcase the reality of the situation. That you can't save everyone. That you can't change the world. That you are bound by society's rules, no matter how unjust they are. But, because they are the heroes, they remain optimistic. That maybe, just maybe, I'll be able to change something, no matter how small.
Anyway, I know this went really off-topic, but these are just my 0.02$. I'm more well-versed in Marvel so I'm probably missing tons of stuff on DC, but that's my personal take on the whole thing. Neither is superior, but, IMO at least, Marvel's the more realistic one. Not the grittier one, but the one who portrays things how they are.