I know this question has been asked before in different ways, but I have specific considerations for my project.
The idea is a project that would need to be highly scalable, the hope of course would be for it to have millions of users at some point (of course I know long term there will be many changes to increase performance, etc).
Also, I would like to open up the code base using and API and allow 3rd party plugins. With PHP it seems to be easier to get a developer community going, being that it is open source. Would like to have a plugin system and developer community kind of like Wordpress
C# is going to have better performance because it's compiled, etc, and I like the language because it is more structured, etc, with the .NET framework. Of course going with C# has other costs... windows servers are more expensive, SQL Server licensing etc... but it should take less servers to run .NET code, so that may not make a difference on that end.
I can program in .NET and PHP, so it's not an issue of which one I know better. Also, I know their are good programmers for either language, so that won't be an issue. I will also follow OOP & MVC for either language I choose.
Also, I know Dharmesh mentioned he wish he didn't choose C# here
Update: It is a web app (SaaS), It can be used by either businesses or consumers (will appeal more to consumers), revenue will be generated by monthly subscriptions
Thanks in advance.