Some more things that IIS does:
1.) takes up far more resources
2.) adds a whole bunch of new services at startup to slow you down even more, some of which you probably wont need.
3.) lets malicious programs get through its infrastructure and terrorise you, such as code red, nimda.
4.) provide platform problems, i.e things like collaboration data objects dont work on version 4, only version 5.
apache is far better, but unfortunately you have to pay for chilisoft if you want asp parsing. :\
The gui for IIS is hardly anything to write home about. It has a "start" button and a "stop" button and some meaningless stats which aren't much use.
The internet services manager is a bit better and its pretty configurable, but again it makes the whole thing rather heavier than required.
apache just has a popup dos prompt window which displays text of whats happening, which is far more fitting, and to the point.