If there were ever a Sophie's Choice...
I went for Corbin. Better moveset, better look. Has more potential as a singles competitor.
Neither of them is good on the mic. They'll give you the occasional decent promo, but that's about all you can expect from them.
Both have largely been carried by people better than them. Where would Corbin be if he weren't having regular matches with the likes of AJ Styles, Dean Ambrose, Sami Zayn, Shinsuke Nakamura, Dolph Ziggler, and Kevin Owens for the past year? Cass, meanwhile, is exactly what Enzo said he is: a 7 foot catchphrase that Enzo wrote.
Neither one of them should be a main eventer and that anyone in the back is even thinking that is insane. Corbin's ceiling is upper midcard, and Cass should be a life long tag team wrestler that occasionally wins a singles title.