I won't get into my anti-MS rant (!!!), but it is true that more coders are familiar with CGI than with ASP because it's more common and works cross-platform. I have also heard that MS changes their API often; don't know personally if that's true although it certainly is true in their file formats. I have also heard that lots of .NET is vaporware; YMMV.
In my book, that blows MS proprietaryware absolutely out of the ocean, no matter how good its purported features may be.