Steamer much better defender, no contest really
I'd take Darko over Steamer myself. Superior defender against strong players and superior pick and roll defender. I don't see where you got this "much better, no contest really" idea from.
Most of the flack Darko gets is for his draft position and the big contracts he's been given. People should focus on what he actually brings, and he's quite the solid defender.
That said, his work ethic has been questioned, as that's my only concern.