I don't hate Microsoft. I use their products everyday. But, an Apache server is just as functional as an IIS server, but with a much smaller footprint.
A PHP script to generate an interactive web page will be 10 Kilobytes at most. A ASP.net application to do the same thing will be several Megabytes.
Unless one is familiar with building ASP.net pages, and configuring IIS, it can be a very steep learning curve.
Apache takes about 5 minutes to install and configure. There are plenty of sample PHP scripts on the net, and plenty of forums to get help.
ASP.net pages are not easily tailored to do something different, so they are not as easily shared.
I've done both ASP.net development and PHP development. PHP is easier, in my opinion. It is certainly easier for a beginner to pick up.
I have never programmed in PHP , thats why i was thinking of developing in ASP.net 