I'd say IW, obviously. BP outperformed expectations greatly at the DBO, but was just seen as another big standalone MCU to the rest of the world. IW, on the other hand, has a good shot of overtaking BP at the DBO, and will 100% overtake it at the FBO, probably by ~60%. If the film is really good, anyway, which I expect it to be at least a decent flick.
And it also seems like it is breaking all kinds of preorder records, as well. Should do at least ~$1.7B.