In my opinion there aren't any real advantages to an overdraw nowadays. The original intent of them was to allow shooters to use a shorter and lighter aluminum arrow thus giving them more speed. Now we have ICS carbons which, at their full length, weigh the same or less than an overdrawn aluminum. If you were to stick the typical ICS carbon in an overdraw setup then you will probably end up with an arrow that is too light in overall weight for your grains per pound of draw weight ratio.

Hope this helps.