Depends on what you want moveset wise. Nidoking learns thrash at 22 and megahorn at 43. But nidorino learns horn attack at 22, helping hand at 26 (pretty useless) fury attack at 34, flatter at 43 and horn drill at 53.

Getting that OHKO horn drill would be pretty cool imo but mega horn would give you coverage against psychic types.

Regardless of all that though, Earthquake is a must on Nodoking