Both Yan and Pico are pure IOC container focused on dependency injection only.

They embrace the "do one thing and do one thing well" phylosophy. Anything that's orthogonal to IOC container is ignored in order to keep the framework as small and fragile as possible.

While Spring is not limited to IOC container. It is a tool kit where IOC container is just one piece among the various services provided by Spring such as data access abstraction layer, MVC, declarative transaction management etc.

The rationale behind Spring is to provide a coherent integration of all the services you might ever need in J2EE development so that you get it all in one shop without the need to cobble together different frameworks.

Yet, nothing prevents Yan and Pico to integrate third party services like those provided by Spring. Nuts has an out-of-box Spring integration package that can take advantage of most of the services provided by Spring.