The difference is where the bottom bracket sits in the shell. The cups on the Phil Wood don't have a fixed position/setting. I didn't have enough patience of pulling the cranks on and off a million times to adjust the bottom bracket to the point where I would have clearance on both sides of the frame.

By purchasing the Campy bb, I simply install it and go. There's no adjustments to be made. The cups can only be in one position.