Brook would fare a lot better due to him having a really good jab and ring smarts, could even go the distance since the fight was at 155 and Cinnamon was far from a KO artist at that weight. Khan on the other hand...
Brook was naturally bigger than Khan so would last longer. Maybe outland Canelo early on too and befuddle him with the Ingle style before getting caught later on Brook used to walk into the ring around 165lbs. Canelo around then was maybe abit heavier.
Both end up getting KO'd. But GGG would KO Khan faster than Canelo. He can cut off the ring and trap Khan quickly.
Always got the impression Brook was juiced to the gills which helped him stay on his feet while GGG smashed his face in. He might have gone the distance back then against a not as ruthless Canelo. Khan on the other hand would have done well to get past round two.