Merckx was caught with 3 different substances on 3 different occasions, I believe Cav is yet to be caught with anything.
Don't get me wrong, probably all of them were/are doping, and I do still think that what Merckx could achieve is absolutely incredible, but he's a bit of a bitter old cunt.
But he's not wrong is he? Even if you added the palmares of Cavendish, Froome and Cadel together, they would be nowhere near Merckx.