Gosh, I like 'em both. It sorta depends on the makeup of your party, and your "pickiness" level. 'Ohana is fun for a bigger group, and it is served family style, which means you can stay in one position as you eat yourself into a stupor. OTOH, Boma is certainly more adventurous by Disney standards, but picky kids or adults might have a bit more of a challenge (altho there's always the chicken tender/mac and cheese option). It IS a buffet, and some folks simply don't like buffets.
If it were just me dining alone, I'd do Boma, 'cause I like experimenting while eating, but if I've got the rest of my family in tow, we'd do 'Ohana.