User blog comment:Legionaire22/Why Horus Why?!/@comment-9734625-20130215120924

Long Hair: Lion El'Jonson, Fulgrim, Leman Russ, Konrad Curze, Sanguinius, Magnus The Red (6)

Bald: Perturabo, Ferrus Manus, Angron, Mortarion, Horus Lupercal, Lorgar Aurelian, Vulkan, Alpharius and Omegon (7, if Omegon is not counted)

Neither: Jaghatai Khan, Rogal Dorn, Roboute Guilliman, Corvus Corax (4)

So, overall, there were less Bald Primarchs than there were Primarchs with hair.