Recs.
Updated
Specs
Pros
Pro Components are more structured and thus have more inter-compatibility
Components can be javascript, style and markup, they are bundled in a way that makes it possible to load in entire UI chunks. This means less flexibility, but the components that are available are easier to work with.
Pro Designed with ES6 modules and Web Components in mind
Component is designed as a current-day solution for the currently proposed ES6 modules and Web Components, making it more in-line with the direction the web is going in the future.
Pro Encourages simpler and smaller components
Components are encouraged by convention to be small and single-use, meaning that the packages in the community's ecosystem are easier to use and combine together. More complex components use dependency resolution to compose smaller components so that components stay limited in scope.
Pro Easy dependency management
Component provides you with a flat dependency tree. This results in easy dependency management. A flat dependency tree is important for file size optimization, so you don't end up loading multiple copies of the same library, or deeply nested dependencies that bloat up.
Cons
Con No longer maintained
Component is no longer being developed/maintained, so there will be no new features or bug fixes.