Hooray, a dining question I feel like I can actually answer. I have been to all 4 of these.
Boma: We don't like it, and I think we're in the great minority here. After hearing all of the hype throughout our planning, this place just did not blow us away. We like "interesting" food and thought this meal was just okay. Our server was really hard to track down for drink re-fills. If you're looking for a quite meal, this is not the place for you - it's LOUD - but I think this is due to it being a very popular buffet.
'Ohana: One of our favorites! We've been there twice. We think the food is great and the atmosphere is fun. Like Boma, not the place to go if you want a quiet meal. The service both times was excellent - here they bring the courses to you and sort of use a "team" approach. We love it. Keep in mind that this is a very hard ADR to get.
Sanaa: Another favorite! This is a traditional sit-down meal. We've only been here once, but we were very impressed! The food and service were excellent and if you're lucky you may get a table with a savanna view.
Jiko: Our favorite restaurant at WDW! Again, interesting and excellent food with great service. A traditional sit-down meal and the place to go if you want a quiet, romantic dinner. However, since you are on the dining plan, keep in mind that this is a signature restaurant and you'll each need to use 2 Table Service credits for this meal (where the others you asked about are 1 TS credit). It's absolutely worth it, in my opinion. We've been here 3 times and it's been great every time.
One other thing to keep in mind is that travel time to these places will be long since they are all at resorts.
I think it just comes down to what kind of atmosphere you want, since you like both buffets and sit-down meals. If you want a quieter meal, I'd go with Jiko. If you want a little bit more of a livelier environment, you can't go wrong with 'Ohana or Sanaa. Happy planning! :wave: