Unless it's in frames, you're going to have a problem with either approach as a web app. You'd be giving exactly 5 seconds to type a message, unless you do a JavaScript SetInterval/ClearInterval to pause the refresh on mouse activity in the textfield or something. And maybe save the chatfield into a cookie so the user never got hosed by walking away for a minute.

I did a web chat in an iframe (so the parent didn't have to reload) that was strongly based on techniques in Stein's Network book that ran from a daemon. It was like the PM one, reload on "submit/refresh."

POE is good for this stuff too, regardless of environment.