Personal preference here since I haven't been to the world yet. We booked Boma for breakfast because of the menu and we are only willing to do buffets for breakfast.
We haven't done breakfast at Boma, but the dinner buffet is great . I've read many great reviews on the breakfast, so we've got it on our list of ADRs for our trip in December.
I've done both meals multiple times and prefer dinner. Breakfast is good, but has more of your standard fare. I like the more exotic and interesting foods you can get at dinner.
We went to Boma for dinner during free dining last year and I enjoyed it very much. There was a lot of new things to try. This year when we go back, we are going to try the breakfast. After reading someone's dining report - I couldn't resist.