Personally I like PHP better because it's free, has a nice/easy/powerful syntax and well, it's what I know more, and glad I chose to use that language for my sites. The native platform is also a ...

ASP enforces a more structured coding environment than LAMP, although the coder/programmer is ultimately responsible for any web development design, regardless of the tools used to build the site.

Depending on how you're planning to implement it (if it's a service and not an application), Web API might make more sense than an MVC app.