When comparing Topcoat vs Cirrus, the Slant community recommends Cirrus for most people. In the question“What are the best minimal CSS frameworks?” Cirrus is ranked 15th while Topcoat is ranked 19th. The most important reason people chose Cirrus is:
Supports both Flexbox and CSS grid making it a great modern choice for designing web apps.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Focused on performance
Every Topcoat component is built with performance in mind. Most of the stylesheets are small and do not take too long to load.

Pro Supports Flexbox and CSS Grid
Supports both Flexbox and CSS grid making it a great modern choice for designing web apps.

Pro CSS Only
No additional JS/jQuery required to use.

Pro Mobile Responsive
Extremely responsive and supports many smaller screens.

Pro Open Source
Open source and quite actively maintained on Github.

Pro Lightweight
Much smaller than Bootstrap with just as much flexibility.
Cons
Con Not so impressive design
But it is themeable.
Con Some issues with typography
For some components the text size is quite small, while for others it's too light over a light background, making the text harder to read.
