Well you'll probably get about 50/50 on this one! I prefer O'Hana hands down. I love the Polynesian Resort, I love that at some tables at O'Hana you can see the castle at MK. My two kids (9 and 11) loved the fun games they played at O'Hana, coconut races and the like. I also preferred the food hands down at O'Hana. Everything was delicous. I enjoyed just sitting, enjoying my meal and not having to get up to visit the buffet. And the buffet lines at Boma the night we went were crazy. Another great thing about O'Hana is that you can ride the monorail to MK or Epcot after dinner which is nice. If you don't have a car, Boma is a bit more complicated to get to. We will definitely be returning to O'Hana. In fact we have an ADR there for next month and are eating there the night before we take our Cruise in September. I asked my husband and kids which WDW restaurant they would all choose for our one night at WDW before our cruise and they all picked O'Hana.
I liked Boma okay, but it was just a crowded, very noisy place. Some of the food was good, they had wonderful prime rib and the desserts were delicous. However, some of it, the salads in particular I did not like. I am glad we tried it but we won't return. Too many other places we like better! And of course other's will have the exact opposite opinion of mine, so good luck with your decision!