In my eyes the two biggest CSS frameworks would be Bootstrap (obviously) and to a much lesser degree Foundation. Fortunately these two are almost exactly the sa

In my eyes the two biggest CSS frameworks would be Bootstrap (obviously) and to a much lesser degree Foundation. Fortunately these two are almost exactly the same in terms of what they achieve and how you integrate them into your app. The decision you have to make is whether you prefer LESS or SASS for a CSS pre-processing language, whether you like the saturated gradients and rounded shapes of Bootstrap or the boxy but shinier theme of Foundation, and other quality of life (for the developer) and aesthetic preferences. I prefer Foundation due to my preference of SASS over LESS (I was also personally convinced of the benefits of SASS and Compass over LESS by Brandon Mathis and Chris Eppstein) and because it also looks unique in an online world plastered in Bootstrap and other similar-looking frameworks.