Difference between initialize a string to "" or to "".ToString() - Which one should I use?

Question

How should I initialize an empty string in C# and why? Which one is faster?

string myString = "";

or

string myString = "".ToString();

Answer 1

String.ToString() just returns the string itself :

    public override String ToString() {
        Contract.Ensures(Contract.Result<String>() != null);
        Contract.EndContractBlock();
        return this;
    }

Which means string myString = "".ToString() is pointless. After all, it's already a string

In fact, given that strings are immutable and, in this case, interned, "" is the same string instance returned by String.Empty