Not the best comparison, Ferrari had slightly taller RW frontal projection. In any case, not what I meant also, forgot to write "RW angle" regarding the inverted scoop on Merc RW. Just a quick CFD to demonstrate what this scoop means for front-view pressure-plots.
Numbers are useless, since they depend on specific aero foils, but I believe everyone can understand the difference the scoop makes. Both for lower drag and lower downforce. The same goes for airbox drag/surface area, which is clear as day...