When comparing slim.js vs Blocks.js, the Slant community recommends Blocks.js for most people. In the question“What are the best JavaScript libraries for building a UI?” Blocks.js is ranked 10th while slim.js is ranked 20th. The most important reason people chose Blocks.js is:
Blocks.js is just 16.5KB minified and gzipped. So it's pretty small.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Easier to learn and use
Leverages web components, uses the platform, reduced weight.
Pro Small footprint
Blocks.js is just 16.5KB minified and gzipped. So it's pretty small.
Pro Modular structure
Apps developed with blocks.js are modular in structure and make use of reusable objects. This makes these applications very maintainable.
Cons
Con Relatively new
Blocks.js is a relatively new library. It doesn't have much support and there re not many people who use it. So if you run into any problems it would be hard to get solutions.