Sorry, but Krstic is nowhere near as good as Perk. If he was, the Thunder wouldn't have given up him, Green, a #1, and taken on Nate's salary to land Perk.
Krstic is a better shooter than Perk. He's an inferior defender and rebounder, and he's less efficient offensively. Even after his return from injury, Perk was playing better than Krstic.