Krstic is not better than Perk, and it's not close. That's where you'll lose this argument. I think Green over Nate makes up the difference between Perk and Krstic, but there's no way Krstic is better than Perk.
But people are sleeping on Krstic. I think a lot of posters are going to be very pleasantly surprised by what he can do. Again, I'm not sure why everyone seems to have forgotten Krstic since he was the starting center on our division rival for like 5 years, but the guy can do more than just shoot offensively. He has a great midrange shot, but he's also very crafty around the hoop and is a very clever offensive player. I think he'll be great next to KG, he'll get a lot of easy buckets with KG's and Rondo's passing. Buckets that Perk doesn't finish.