Harley Quinn is an expert gymnast (she received a scholarship to Gotham State) and trained in the field of psychoanalysis. Other than a few toxin immunities, Harley doesn’t have powers of any sort. Mystique, on the other hand, has some of the most impressive powers in the Marvel universe. She can psionically shift the atoms of her body to duplicate any humanoid of either sex, wearing any kind of clothing. She can essentially become any person she wishes. Along with this, Mystique is immune to poisons and drugs and doesn’t age. Her abilities have allowed Mystique to go undercover in any number of situations and give her a definite point in this category.
Harley first showed up in BTAS in 1992 and by the next year made her first comic appearance in The Batman Adventures #12. She has also made appearances in numerous comics and especially video games, including Injustice: Gods Among Us, the Arkham series, and Lego Batman. Harley appears in some animated films including Batman Beyond: Return of the Joker and other animated shows besides BTAS including The Batman and Batman: The Brave and the Bold. She was also on the short-lived live action TV show Birds of Prey, portrayed by Mia Sara.
Mystique first showed up in Marvel comics in 1978. She has made appearances in different animated television shows including X-Men and X-Men: Evolution. Mystique has a strong record in live-action films, being portrayed by Rebecca Romijn in the original X-Men trilogy: X-Men (2000), X2 (2003), and X-Men: The Last Stand (2006). Her character has had a resurgence with the newer X-Men films, X-Men: First Class (2011) and the upcoming X-Men: Days of Future Past played by Jennifer Lawrence. Mystique is also a popular character in video games such as X-Men Legends.
When it comes to social relevance it’s hard to beat Harley Quinn. Go to any comic convention and you’ll find at least a handful of Harley’s. She’s a fan favorite for memorabilia, art, and especially costumes. She’s loved among gamers, comic-book readers, and BTAS viewers alike. As cool as Mystique is, even her increased film relevance can’t top the power of The Joker’s #1 girl.
Point: Harley Quinn.
This was an especially tough battle with two feisty and sneaky ladies who constantly keep audiences engaged with their on and off affiliations and unique physiques. At the end of the day, it’s Harley Quinn’s fame and strong fanbase that not only got her into the comics, but won her this competition as well.
WINNER: Harley Quinn!
Background, Affiliations, and Apparel/Weapons at the source
EDIT (since no one will bother reading): These competitions are about who is a better character overall, NOT just who would win in a fight.