oh..I forgot.. a reverse sidecut ski traditionally weighs less than most traditionally shaped skis that are 110mm underfoot. This is because ski weigh is traditionally carried in the tip and tail of the ski. Because that weight is further away from your foot (and the fulcrum of your binding) it causes the ski to feel heavier than it is. When you use a reverse sidecut ski for touring the weight is under your foot. This means that you aren't pushing and pulling weight around with you.
Also.. anyone can ski powder on a 100-110mm ski....its just more fun on a RR ski.
One last thing. I find that I don't mind having a little extra weight. More weight = Stronger. Stronger = Better Skier.