I'm a dyed-in-the wool emacs user (and have played with vim quite a bit) but there's really no comparison between the "completion" vim and emacs offer and that

I'm a dyed-in-the wool emacs user (and have played with vim quite a bit) but there's really no comparison between the "completion" vim and emacs offer and that provided by IDEs like VS and Eclipse. They do quite a bit of static analysis and do context-sensitive completion which is extremely helpful when the standard library for your language has a ridiculously bloated API (like, for instance, Java and .NET).