Except Morgans don't have a sliding pillar system - the pillar is fixed. A mis-nomer...
Lancia did actually have sliding pillar suspension (pre-war?) for a while.
Advantage? Camber remains the same, so no matter how much the suspension compresses the tyre footprint remains the same. Simplicity could be argued as another...
Hi Graham
Do you recall the debate on EgoMog? Arguments put forward that if you consider the wheel as the base datum point as it follows the road its the car and therefore the pillar that does the moving, one bright spark even argued that if the car is stationary and you push the wing the stub axle stays still and the frame and pillar moves proving its a sliding pillar. I think the same person believed everything revolves around the earth mind you, me, I just checked to see if my ears were bleeding yet and hit delete.....

Happy days!