Corben more often than not is either an American soldier or small-time crook/thug before becoming Metallo, so Ritchson would feel more comic-accurate to me. I also have less than zero desire to see Shazam again any time soon lol.
That said, I don't really wanna see Metallo either. Wildly overrated Supes rogue, imo. Could see him as a basic baddie he's fighting when the movie opens or something, but he'd be a terrible Big Bad. There's a reason he's thrived on TV - episodic villain or lower-level henchman at best.