They are two VERY different restaurants.
Boma is a large and extensive buffet. The room is large and noisy. The meal will be "reasonably priced" particularly if you are a big eater, and will include everything but beverages. Expect lots of families and bright colors.
Jiko is a "fine dining experience" expect wonderful food, an extensive winelist, great service, and a bill that is corresponding. The decor is dark and the restaurant cozier and quiet. Most guests will not need booster seats (though like almost all Disney fine dining restaurants, kids are present - and sometimes in quantity).
(I didn't like either, our Boma experience was disappointing because we had higher expectations than could be met, and our Jiko experience was similarly disappointing, our waiter was not great, and I think I ordered wrong - food was good, but not to my taste. At some point I'll try Jiko again, and maybe even Boma, but I won't be in a rush to go back to either. I will visit the Animal Kingdom Lodge, however, get a drink, and watch the animals - the Lodge is incredible!)