Keep giroux and carter (you'll get goals and assists from them combined). Plus giroux and carter both have dual positions. If you do the trade you'll be killer in the assists category, but thats about it.
dont do it. points wise theyll be close but the thing is getzlaf and koivu are set up guys. giroux + carter will end up with plenty more goals which will means more total pool points for you. forget combos, they dont matter.