Love them both but I'd pick Ohana UNLESS it is your only night to see the fireworks and you won't be able to get back to the park in time. Even though you can get a really good view of Wishes from Ohana's main dining room, you can't clearly see MM&Y; not enough for the details. And I think I am more taken with that show that with Wishes!
So if you can see MM&Y and Wishes later that night, or on another night, then keep Ohana. But if this is going to be your only chance at them for this trip, drop Ohana and take the Dessert Party instead.