1. More Successful Plans While both Robotnik and the Didact were thwarted, Robotnik actually managed to accomplish a lot more before most of his fell apart. He has blown the moon in half, broke the planet apart, revived countless mythological monsters to do his bidding, built an amusment park out of several alien worlds and even manipulated time and space. What has the Didact done besides zap one city on Earth and use the Composer to rip off Raiders of the Lost Ark? Nothing. 2. Actual Motivation Sure, his prime motivation in life may be the establishment of the Eggman Empire, but it is a fairly nice goal. And failing that, he has the pursuit of a teaching degree to fall back on. What is the Didact's motivation? Did you read Silentium? No? Well -blam!- off then because that is where it is at, not in some silly place like the game. 3. Better Minions You have to give the Didact props, the Prometheans are pretty cool because they are living organisms that have been turned into robots. Oh wait, Dr. Robotnik already pioneered that concept back in 1991 by turning animals into machines all the while without having to rip off Raiders of the Lost Ark. Oh and Metal Sonic would destroy any Promethean. 4. Better Design Robotnik is modeled after Theodore Roosevelt, the manliest man who ever was in a man. Nuff said. The Didact looks like the bastard spawn of Voldemort and the Cloverfield monster. I rest my case.