I think it's safe to say that what you just read is a minority opinion. Both restaurants get great reviews from most people.
I can't speak to Boma, because I haven't eaten there yet. I did walk through it after Jiko's one night, and can't wait to try it on Friday. The food looked great. I have eaten at AP and enjoyed it extremely. I had a filet with crab meat, and it was delicious. One of the best steaks I've ever had.
What you want to do is decide which atmosphere you want, because they are very different places. It's awfully hard to say you'll enjoy one more than the other, because it depends on what you want. Jiko is a much closer comparison to AP than Boma is.
If you want to sit at your table and have very good service, you pick AP. If you want to get up, try a lot of different things and experiment, try Boma. (You'll save money by going to Boma, too, I think.)