Best practice and memory performance?

If I have a temp game object or list or anything in a function would it be best practice to call it each time I call the function or should I just have a temp global variable that assigns a new value?

      private int bar = 0;
      private void Foo(int value)
      {
         bar = value;
      }

Or

       private void Foo(int value)
       {
          int bar = value;
       }