Chows are the only dogs that turn on their owners regularly. They don't have the trust that other breeds have. They can't be trusted the way other breeds can.
Pit bulls-its in the way they are raised. Yes, they CAN be vicious, any dog can, if its mistreated.
The Chow is more the concern.
I knew a pit bull growing up that was the sweetest dog ever. The Chows I've known were plain mean and unfriendly, all of them.