I read an article recently that pounded out the math on having a reroll against equal defense dice versus having one more attack than defense dice. He called it an overpower die or something I can't remember, but the long and short of it was that it's ALWAYS better to increase your attack vs defense dice differential versus having a reroll. I think the math was something like at extra die over your defenders number increased your damage average by a little over 100%. And Outmaneuver pretty much guarantees you that extra one, if not two or three dice over the defenders number.
And my favorite part? Outmaneuver totally negates C3PO on 1 agility ships where he gets used most often. No dice to roll means no guessing the number of evades.