If by "all the aluminum goodies" you mean water pump and housing also then there is gonna be less than 20# differance and the advantage may actually go to the BB because the weight will be slightly lower, either way it will be very slightly different. As for witch one makes more power it will depend on more than just saying aluminum BB heads VS W2, a stage V is aluminum but so is a stealth and a good W2 can make more HP than a stock stealth head so we would need to know more about the two combos.