Long a favorite of mine, Mithril really shines in these metrics.
The shortest download+parse time (~200ms), the shortest parse time (80-100ms), the shortest initialization time (almost negligible at 10ms), the best performance on the XL thread (1.3 seconds!), and the best performance on the moderate thread (200ms).
Render functions feel a little messy
Mithril transforms your render functions/'templates' into a mass of parentheses and rectangle brackets.
I haven't used MSX, but I would likely do so, and I'd likely incorporate it into a build system that includes a template manager (that is, no inline MSX for me).
Mithril thennables take two functions as optional parameters, success and error. Fortunately, enough people have been after them saying "Please just do promises like everyone else does" that an upcoming version of Mithril will have fixed this.
If you are rendering into document.body with the router, you'll want to put your script tags in the body tag. I forget why exactly, but it has to do with document.ready and is amusingly the exact opposite of what you might experience with Vue.