Kaneki has been through a lot. From being a victim of circumstances to Hide’s death, life was never easy for him. Yet he cruised along. So for the sake of his team mates, he held back his real self and got his shit together.
But what really proved Haise Sasaki as Kaneki was the cracking of fingers at the end of the first episode.
The cracking of fingers symbolizes two things, the abuse and abused, i.e the victim. Jason behaved in a psychotic way, not because he was born with illness but because he was tortured by a violent investigator.
The cracking of fingers is a portrayal of strength and dominance in a fight.
What makes Haise Sasaki awesome as compared to Kaneki Ken?
We now know that both of these guys are the same physically. But there’s still a lot of mental and psychological factors to be considered. In the later part of manga, we know that Kaneki actually lost most of his memories.