I can see the argument that Raffy COULD gain weight and hurt his career. However, a lot of the negative perception is due to the shape of his face and the fact that he's just generally a bigger guy. I think if he didn't come right after Pablo Sandoval, we wouldn't be as concerned.
I think Betts plays hard, but I wouldn't say he's as reckless as Pedroia, who often had shorter seasons due to nagging injuries and had a knack for diving headfirst into first base or whatever.
I think there's a bigger risk that a guy like Casas doesn't age well. He's already had a few injuries, carried a lot of weight when he was younger and is generally unathletic. If I had to bet money on someone having a shorter career, it'd be him.