I don't think there is a performance aspect.
However, I find the Razor syntax beautifully terse. The HTML is far more prominent with Razor, which is what you want when you're developing HTML views.
In various MVC frameworks, view development encourages and requires code written directly alongside markup. Because the ASPX view engine was not designed with this goal in mind, the ASP.NET team decided to build an entirely new view engine with a code-focused templating approach. The result was a more intelligent parsing engine that is able to very easily figure out where code stops and where markup begins, without the developer needing to be very explicit.
There are even open-source view engines, that you might want to look at. For example, Spark View Engine.