You are right some places your chance is better. However Ohana isn't one of them.
Ohana is very very very popular right now and the chance is very slim.
Not saying don't try, but don't get your hopes up. Make sure to have back up plans.
The only reports I have heard of a sucessful Ohana walk up was arriving before opening and waiting 2+ hours to be seated.
(that is insane in my book, Ohana is good but not worth losing that time)
Good luck, as PP said, keep trying to score an adr before you go.