Which one to choose PHP or ASP.NET given ASP.NET 5 promises cross platform support

Here is my scenario and would like to your opinion on which one to learn next PHP or ASP.NET:

1. I already have been programming in C# (Winforms). So would like to keep programming in Visual Studio environment unless the cost of sticking to Visual Studio is too high compared to LAMP approach.
2. Earlier ASP.NET hosting cost was a bit higher than PHP but ASP.NET 5 promises to be cross platform. This I hope would mean that all the tools with ASP.NET would run on Linux with no issues.

So overlooking all other advantages or disadvantages of either PHP or VS and sticking to the cost factor what in your opinion is the best way forward?