I'm like everybody else, either one will make a fine bow, but I'll take osage here in the land of wring-water-out-of-the-air-with-your-bare-hands. If you can keep the hickory dry, it's great. But even with a good finish, it'll eventually reach an equilibrium with the local humidity. If your house is centrally heated and cooled, it'll help to keep wood pretty dry. One thing I've noticed is that even though we have hickory growing everywhere here, most of the local Indians greatly preferred locust for their bows. I would say that the main reason is that locust is an oily heartwood very similar to osage in it's ability to not pick up a lot of moisture in a humid environment.