Interesting, I don't have much experience with either, but I thought Mithril was kinda succeeded by Aurelia, which makes it a less attractive choice for a new project. Good to see there's still stuff going on.
You're probably thinking of Durandal, which was the predecessor of Aurelia (along with some brief history involving Angular, IIRC). Mithril is an entirely different project by different people, I believe.