I`ll go for Dr. Freeze. In my opinion more songs like "Blue Gangsta", "A Place with no Name" and "Break of Dawn" could have contribute to a great album, that Invincible is not.
The chemistry with Rodney Jerkins and LaShawn Daniels etc did not really work. I like their songs, especially Unbreakable, Invincible, YRMW and Threatened. But they are not as great as what Michael did with Teddy Riley for Dangerous.