Akuma will be familiar to fans of Street Fighter, essentially being a kind of demonic Ryu, while Taskmaster is a ninja created by Marvel. Akuma will be unlocked with 2000 Player Points, while Taskmaster requires 8000 - earned by playing through the Arcade mode, playing against friends and completing challenges.
Marvel vs. Capcom 3 is due for release on Xbox 360 and PS3 on February 18.
While Taskmaster isn't a mainstream Marvel character, fans of Deadpool's comic will be excited by his inclusion. Akuma is a more well-known character and if he wasn't included it would feel like a massive omission.