No. There is no difference1.
In both case a new function object is created (through a Function Expression), assigned to a variable, and then mutated through a property assignment.
The only difference is one function has a name assigned, which may prove useful: see
myFunction.toString(), or access to
myFunction from within the function scope. Since it was a Function Expression (as opposed to a Function Declaration) the name has no bearing on variables in the defining scope; 1caveats for legacy browsers are covered elsewhere.