I'd say it depends on your background and how much money you have to throw around too. ASP.net has some great features but you may not even need them depending on your project. The tools are expensive, the hosting is expensive.
PHP is great because you get a lot for free, but there are trade offs.
Personally I like .NET better because thats what I started off with, I feel like I can do more with less, but thats a personal preference. I'm sure some vet php developers feel the exact same way too.