In the technologically-advanced Academy City, millions of students study superhuman and psychic powers. Judgment, a group made up of specially-trained students and adults, helps combat threats to the city and its people by helping apprehend power-wielding criminals. Mikoto, Kazari and Kuroko are three friends who juggle school and Judgment, all the while learning how to best use their skills. Together, they will help keep Academy City safe from the bad guys and have plenty of fun in the process.
Ahh, the life of an elementary school student. Though Chika, Matsuri, Miu and Ana should focus on schoolwork, they’d much rather have fun instead. Whether it’s outings with 20-year-old-chain-smoker Noboe, holding each other hostage or learning to speak English with Ana’s foreign-born skills, there’s never a dull moment in the life of the girls. Join this cute quartet as they do cute (and often devious) things in cute and quirky ways!
I know this is a strange recommendation, but bear with me. While Railgun has a lot of action and superpowers, it and SM have a very, very similar group of friends with plenty of slice of life moments. In addition, Mio in SM is a carbon copy of one of the characters in Railgun (both equally as annoying). If you liked the dynamics of the group in one, check out the other.
300 km south of Tokyo lies Itogami Island - a man-made landmass that’s been authorized by the government to house spirits, vampires, mermaids, and other magical beings who’ve been pushed to the brink of extinction. Kojou Akatsuki is one such resident who used to be a typical high school boy, until an incident 3 months ago turned him into the Fourth Progenitor - a powerful vampire - against his will. And while he’d rather stay an anonymous teenager, things change when Yukina, a sword shaman from an anti-terrorism agency, arrives with intentions to watch over and potentially eliminate Kojou...
Each anime centers around a group of teenagers who are enrolled in a school, and live in a city that is specifically designed for people with supernatural powers. In Railgun it's humans that have extraordinary powers, whereas in Strike the Blood there's more of a fantasy element where the inhabitants are all supernatural beings such as vampires, but both contain magic users.
Both can be pretty serious when they want to be, but have their cute, fun sides as well, with a dash of fanservice added in for good measure. The action in each is also well animated, especially in Railgun.
Fans of one may find the other appeals to them.