This same debate comes up in the skydiving community as well. Heavier jumpers tend to fall faster, which is why they even make weighted belts so RW teams can match fall rates.

The heavier an object is, the higher its terminal velocity. Terminal velocity occurs when the gravitational force (parallel to the direction of motion) equals that of the air resistance. The heavier something is, the higher the gravitational force will be (m*g). Thus, the higher the air resistance will have to be in order to match it.

On slopes, gravity isn't pulling straight down, so you have to use some trigonometry to scale down the gravitational force, which also scales down the terminal velocity (that's why you can go terminal at 30-40mph versus 120mph straight down).