Well, Black played the opening horribly (putting a bishop on c5 is fine, but it absolutely requires keeping the stronghold on e5).

Black is already hopelessly behind in development, so his 9...Bxd4 is a good practical choice in a lost position: He just hopes that you go mad and play some nonsensic sacrifice. Simplest winning move after 9...Bxd4 is of course 10.0-0-0, but your 10.Nb5 looks fine as well. I think that almost every move here is winning for White, excluding the one you suggest: 10.Bxd6 can be calmly ansered by 10...Nf6 (white is still better, of course).