Oscar's Rivas partial amateur record was 17 fights with 8 won via points,4 won by ko or tko and lost 5.
Andy Ruiz's partial amateur record was 12 fights with 2 won via points,4 by ko or tko and lost 5,1 loss via TKO, also holds 1 walk over win.
Ruiz is much more proven in the pro ranks. I've just got big doubts that Rigas can succeed in the pros at his size. Ruiz until proven otherwise.
Tough fight based on styles, but Andy has been in with the better competition and it's arguable he beat Parker in his last fight, so based off of that I'd go with Ruiz.
It's good to see that Ruiz has gotten a lot of posters respect on here from the Gallant effort he put forth against Parker! Kudos.