The Wave breakfast is our absolute favorite meal on property and usually the only TS breakfast we do. That being said, the two are completely opposite experiences so it depends what you're looking for. If you want something highly themed, more kid-friendly, AYCTE, characters, etc, go for 'Ohana. If you want more subtle, but still beautiful, theming and a quieter meal, go for the Wave.
Some other things:
- The Wave does have a buffet as well, but we usually order off the menu.
- Even though the Wave is quieter, I don't mean to say it's stuffy or not kid friendly (not sure who's in your party). There are always families there.
All that being said, if I were you I'd probably pick 'Ohana since you will be doing both for dinner later in the week. I'd want to experience 'Ohana for two meals rather than the Wave since the two meals seem to be two different experiences at 'Ohana more than they are at the Wave. The Wave is the same restaurant throughout the day whereas 'Ohana has the character aspect in the morning but not at night.
These are just my thoughts.

It really depends what you're looking for!