Golovkin is the bigger hitter so that obviously makes Canelo's chin better. . Unless you want to argue that GGG got hit with way more power shots than Canelo did. In that case the argument for GGG easily winning goes out the window.
Toney wasn't knocked down by Roy Jones Jr. He was hit by a punch while they were both clowning and stumbled back. Do you think a prime Roy Jones Jr wouldn't knock GGG stupid?
At Middleweight only its Hagler and GGG since a young Toney was flash knockdown by Johnson. But P4P its Toney by a mile