Ok listen. I have seen many a report that puts the performance of Microsoft's IIS webserver above the Apache 1.3.x webserver software. It is a known fact that it is more efficient. Keep in mind, I am a linux junkie and hate Microsoft, but I am not embarrassed to face facts.
But here is another fact, Microsofts webserver software costs $1000+ for each computer it is installed on, and has a multibillion dollar company that develops it. Meanwhile Apache is free. Also Apache 2.x fixed many of the performance problems that 1.3.x suffers from. Did I forget to mention that Apache has suffered far fewer critical flaws than IIS, and they have been detected and patched in a much shorter period of time due to the fact that it is open source. Oh and Apache is the #1 webserver in the world. Not bad from a company no where near the size of Microsoft.
Now even though Microsoft IIS is more efficient than Apache, you have to really look at these stats and question their validity in real world applications. Huge websites such as Amazon.com use apache every day with absolutely no problems. So you really have to wonder if these tests mean anything at all.