One has this incredible killer-feature you didn't know you want but is way too strict in how you can use it. The other has no outstanding feature and somehow works but is actually older than Web 2.0.
Yet another depends on jQuery UI that you desperately want to remove but don't know how.
Well, basically one is worse than the other.
This feature is so commonly used, but what exactly would you need to accomplish autocompletion? Preferably one that is capable of AJAX? Let's see in this quick and dirty attempt.
This website has no builtin AJAX responses, so we're gonna fake that part, though. (There's always a catch with autocompletion, eh?)