A tough question, not a lot of information ... in ASP.NET books, a compiled language will give you a small boost to performance, rather than an interpreted language like the old asp, php, etc.
The reason for this is that compiled languages are faster because they have already compiled everything compared to a php page that needs to be read and compiled on the fly. But PHP also has some tricks to improve speed by compiling it ...
In the end, the speed of ASP.NET and PHP should be the same.
So this should not be your main problem. You should focus instead: