They are both broken equally man
After Kuzan took out Garp, would be closer to the emotions Kizaru felt when he killed VP. You are misreading Kizaru's words. He pulled through to kill VP despite him being torn apart inside, but it's confirmed he was completely broken after that fact. Except for him the arc didn't end like it did with Kuzan, Luffy was still around, Kizaru just used that to time himself out, he was a shell of himself.
During Garp vs Kuzan, and Kizaru vs Luffy rd 1, you can definitely say they were equally torn though yea.