while there could be some rather interesting discussions on the differences between skier and boarders in bumps, I think its kind of a shame to know that someone from PSIA's forums, copied the post, and repost it here, and then went ahead to make comments that could very easily be construed as inflamitory and insulting, I think the "Professional" part of PSIA (which includes AASI) has been forgotten.
Now I have always looked at bumps as a way to diferenciate between a good snowboarder and a great snowboarder. Yes there are differences, but I have seen a good many boarders rip bumps that I am uncomfortable finding a line in. Any good skier or boarder has to be able to adapt to their surroundings, and bumps are a perfect example. Boarders do help form bumps, and can be very good at (and sometimes better) at forming good lines (while the bumps are forming).
When you say "A skier is in a better body position in relation to the fall line (hips shoulders facing down hill) allowing for more efficient movements." Yes this is true for higher level bump skiers, however I would argue that the average Joe Schmoe fighting his way through a bump field does not even come close to keeping their body in the right position, and does not make efficient moves, however, a boarder on the other hand, by being with their shoulders lined up more with the fall line, seem to have an easier time keeping their shoulders squared to the fall line (or close - basically, they tend to hold a better and more efficient body position).
Now something else to take into account it leg/foot rotation with skiers, I always see people over rotating their legs and feet in the bumps, which minimizes their ability to maintain a proper balance in the bumps. However, on a board, often times, you see an average skilled boarder, standing on his/her front foot, and swinging the tail to turn through the bumps. While this may not be the proper or effective way to board on the groomers, it seems rather fitting in bumps, they stay forward and by the way the are turning, they are typically maintaining a more balanced stance than a skier whos feet are turned sideways.
Another thing to keep in mind is the general body position. On skis, most people have a hard time driving their tips and maintaining a good forward pressure in their boots allowing them to stay forward, but on a board, by maintaining a stance that puts one foot in front of the other in the fall line, it is possible for them to drive the tip of the board better than an average skier. On a board while the feet are strapped in, you are more able to keep the board in contact with the snow while going over inconsistencies (like bumps) because you are able to have 1 pressure points (spots where you can apply pressure to make the board have contact). However on skis, you only have on, and its central, therefore, I could see how it is possible that for an average skier and boarder in the bumps, the boarder might actually have the advantage.
But like I said, when you look at advanced/expert level bump skiers, you have to say that the skiers are in a better body alignment for the terrain.
Just my $.02