Out of all the previous Brainiac designs, definitely the all-metal skullface robot. I feel the explicitly bald* flesh designs make Brainiac look either too much like Lex Luthor or too much like Darkseid or Mongul. That robotic Visage is his/it's most unique presentation.
EDIT: that's another thing: Luthor, Brainiac, Darkseid, Mongul, Parasite, Doomsday, Mxyzptlk ... they're all bald or balding, while Kal has a perfect coiffure of locks. That is some serious ... hairism? Baldism? Whatever, some serious prejudice against the follicularly disadvantaged. What? Why Yes, I do shave my own head ... why do you ask?