I feel they are very different. I've done both (last year) and I'll give you my opinion of each.
I think that O'hana is a fun dinner because you can go outside and sit on a hammock and watch wishes if you time it right. The food is fabulous. I could drink the sauce that goes over the bannana dessert. It's a beautiful resort to have dinner at. The location can't be beat.
WCC is also fun, but it depends greatly on your server. It's loud, but honestly I've never laughed so much at dinner. Our server was really giving my son the business and she made our evening. Had we not had her I think it would have been on the dull side. The food was also very good and plentiful, but you can get good BBQ elsewhere, not just at WDW
I'd go for O'hanas.