First, for the sake of your barrel and your sanity DO NOT USE A WOOD DOWEL. NEVER. NEVER.
Wood will break and splinter at almost any resistance and then you will have a piece of wood stuck in the barrel and use language that your mother would not approve of.
No, Cntryboy1289, rod steel is NOT as hard as barrel steel, and will not scratch a barrel or wear it in normal cleaning use. Further, steel is hard enough that it won't pick up grit, something both aluminum and plastic are notorious for.
I do agree that jointed rods are bad and should be used only if necessary. Even then, it is a good idea to round the ends of the sections, especially the female end, so the joints don't nick the barrel. This is not a contradiction of what I said about the rod being softer; wear is one thing, pounding is another.
Jim