Any difference here is limited strictly to the compiler; the IL and runtime have no concept of verbatim vs escaped - it just has the string.
As for which to choose: whichever is more convenient ;p I almost always use verbatim string literals if there are unusual characters, as that allows for multi-line strings very easily and visually.
As an interesting case:
bool areSame = ReferenceEquals("c:\somewhere", @"c:somewhere"); // true
which tells are they are exactly the same string instance (thanks to "interning"). They aren't just equivalent; they are the same string instance to the runtime. It is therefore impossible that they can be (to the runtime) different in any way.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…