[skorpioskorpio]

The real advantages to disks are, as stated, the braking surfaces are vertical so they drain off water better, and they are more linear in their action. Drums tend to hit a point of expansion and then the shoes wedge them selves into the drum and they lock up. Also all automotive drum systems I've ever seen use one leading shoe and one trailing shoe, in other words one point of expansion and both shoes sharing a common fixed point.

Before they went to disk, motorcycles, particularly high performance motorcycles used double leading shoe drums where both shoes expanded into the drum at their leading edge and the fixed point of the shoes was 180 degrees opposite each other. This has somewhat better wet performance and is less prone to wedging, because hey suddenly locking up the brakes on a motorcycle is a bit more spectacular than it is in a car.

Anyway, the point is that a big enough drum with the same capability to arrest a given amount of inertia as a disk will not have the same linear application feel to it.