Dis argument is easy for me.
I did some ASP.NET when I was doing my C# course a couple years ago.
My preference does not come down to actual language: In all honesty, I found ASP.NET (using C#) a lot easier and guided than PHP.
I prefer PHP because I like to go to work scruffy, wearing a cap, unshaven, and work with interesting people, mostly old skool hippy nix geeks.
I chose this path as I prefer being in the new media/design world rather than corporate shmorporate. Bleh, what does money have to do with anything? If that is the only thing that counts, then go ASP.NET cos you will get a better job.
I dislike PHP as a language, but I love PHP because of the world around it, if that makes any sense.

peace!
Edit:
i had to add, these days i will only build web apps using a trusted php oop framework. PHP is powerful if used correctly, my advise: use a framework!