Lightweight (~11KB Zip Archive)
Designed for mobile first
Based on Flexbox
Open source on github
More concise syntax. The Class names are short and easy to remember. You don't have to struggle with remembering the names, just add the row class and then the number of columns you want.
The Fontawesome 4.7.0 library is already included in the uncaught.css file, but you can always upgrade it to that latest version, or use any other icon library if you want.