[batista]

For C++ and Objective-C XCode absolutely smokes Emacs with regards to code completion.

True AST based code completion aware of all of your constructs without hacks and kludges like ctags and the like...

[Ralith]

The Emacs code completion I use hooks Clang, which is the same thing XCode does.

[aerique]

Xcode doesn't feel very aware of my constructs since there's so much crap in the completion list. It's not totally useless but could be much better.