An interesting question came up on /r/comicbooks last night: does Marvel or DC have greater diversity in its books? I decided to do a quantitative and qualitative analysis of each company's projected superhero output for July 2013, and while I can't say I was terribly surprised overall, there were some interesting bits of data. The TL;DR for those of you that just want the good stuff is that, percentage-wise, Marvel blows DC away on race, DC wins on GLBT representation, and Marvel barely noses out DC on gender. However, the qualitative analysis mostly goes Marvel's way.
Before I give you the numbers, a few caveats. First, I am not 100% of all the lineups on all of the books, and of those, I do not necessarily have an encyclopedic knowledge of all of the characters on the books; if a character is gay or Hispanic or whatever and I don't have that listed, let me know and I'll correct it. In particular, if someone can give me a breakdown on Legion of Superheroes, I'd appreciate it; however, that book has long been a white kids in space book, so the current numbers I pulled out of thin air for it are probably pretty generous. In a similar vein, for books that I think have a rotating cast, I chose to just mark them down as 0 across the board, since that doesn't affect the percentages either way.
All that out of the way, here's the link to the quantitative analysis. Overall, Marvel has more team books with a non-rotating cast, which gives them a little bit of an edge in diversity there, and DC tends to double down on specific heroes (multiple Superman and Batman books) that hurts them a little bit. On the other hand, Wolverine, Captain America, Thor, Spider-Man and Iron Man show up in multiple team books, so the net effect on the analysis is minimal. It does help to show how many of the established and popular characters are straight white males, however.
As I said at the beginning, Marvel absolutely crushes DC on race. They have a far more racially diverse cast, and they tend to put those racial minority characters in prominent positions, including leadership ones. This is only going to get worse for DC in the fall when Mighty Avengers starts up; Marvel will have the first non-imprint primarily minority team book in years, and that will turn this whole section into a complete rout.
On the other hand, DC, by the numbers, pretty handily defeats Marvel on GLBT representation. It has the only book currently being published that features a solo hero (Batwoman) that is a lesbian, and it also has one of the very few transgendered heroes currently being published in Shining Knight on the Demon Knights team. It is noteworthy, however, that Marvel has a much more even split between male and female gay
On gender, the two companies are reasonably even with each other, percentagewise. Marvel gets a very slight nod there of one percentage point, but it's very competitive. Both companies have multiple all-female lead books, and both of them have prominent female characters in leadership positions on teams and in solo books.
So that's the quantitative analysis, which seems to be pretty even on first glance: Marvel is better on race, DC is better on GLBT, they're even on gender. But then you get into the qualitative analysis, and the whole thing goes pear-shaped for DC. Let's be clear: DC does do a lot of things right here. As noted before, it has Batwoman and Shining Knight, and it has Batwing, a black man, on a solo book. It has Birds of Prey, which, for a while, was the only all-female cast in comics, and it has Power Girl and Huntress on Worlds' Finest.
But then you look at the broader picture. DC does have Batwoman and Batwing, but it only feels safe putting the characters under the larger aegis of the Bat-family; it's uncomfortable making new IP that doesn't have Bat or Super as a prefix, and that includes diverse characters. The Justice League, its flagship team, has one woman and one black man and no GLBT characters. The GLBT characters that it does have, Batwoman and Shining Knight aside, mostly have that as part of their backstory or stories from back when they were on Vertigo titles; Constantine and Madame Xanadu both have same sex relationships in their past, but that's kind of the key word there: past. Removing those two characters from the list put DC and Marvel on a pretty close par with each other.
And then you look at the way DC treats its female characters and it becomes clear that numbers alone can't speak to the issues. One of their most prominent characters is Catwoman, who is basically titillation personified, and whose first New 52 story was... unpleasant on a lot of levels. Their most iconic female character, Wonder Woman, fights crime in a bathing suit. There was a brief attempt to give her some pants, but that met with outrage. Power Girl = boob window for many straight male readers, and there was constant pressure to put her back in the old costume that DC finally gave into. Batwoman, while a prominent lesbian, is a fairly unthreatening lipstick lesbian that's intended to please the straight male demographic as much as the GLBT one. Starfire, who had most of her fame with non-comics readers from the kid-friendly Teen Titans TV show and could have been used to draw young girls into comics, was introduced as an airheaded sex doll in Red Hood and the Outlaws. Let's be clear: there are some characters on the Marvel roster that are problematic (I'm looking at you, Emma Frost), but even Psylocke's costume has been updated to be less offensive these days.
And all of this ignores the fact that Marvel has better age diversity in their cast, from Franklin and Valeria Richards up through the teenagers from Avengers Academy and the X-titles and on up to the elderly heroes or anti-heroes like Magneto and Thunderbolt Ross/Red Hulk. Marvel also has the only regularly occurring heroes with disabilities of the two companies, with Daredevil (blindness), Taskmaster (memory issues), Professor X (paraplegic; also currently dead, but that's not going to stick), and others. Before New 52, DC had Oracle and Cassandra Cain, but they decided to "fix" Barbara Gordon and hide Cass.
Overall, both companies have some improvements to make, and they have both also come very far in terms of diversity from the comics I read as a kid in the 80s. But comparing them with each other, Marvel seems to be doing a better job of promoting diversity and seemingly doing it for the right reasons and in the right ways than DC is these days, with no signs of letting up.
Edit: ThanosCopter at The Outhousers helpfully pointed out that Batwoman is Jewish. I've updated the spreadsheet accordingly.