> Parentheses allow you to leave out the commas between arguments.

You compared the wrong things. The parentheses associated with myfunction aren't doing that.

The reason Lisp is better at passing arguments to functions is that it requires you to add parentheses to every function call. The C-style syntax in your first example is trying to let you do this:

    myfunction(a, a+b, c)

In Lisp, you'd do this:

    (myfunction a (+ a b) c)

C has "saved" you the work of putting parentheses around (a+b) at the cost of making you add commas to everything. Here that's a wash because you needed two commas. But C really did save you three spaces that are necessary in the Lisp. (They separate a from myfunction and + from a/b.)

You could save two spaces while getting the same benefit of losing the commas if you went with

    myfunction(a +(a b) c)