p.1 #2Autofocus differences 100-400 compared to 150-400
I think you mean the OM Systems lenses. I've only tried them at shows or for short times borrowing friends gear. The 150-400 seemed snappier to me yet not a big enough difference that you would miss shots. The faster aperture of the 150-400 will make a difference in low light and be able to AF when the 100-400 can not. By keeper rate you probably mean in focus images. Keeper rate is about good photos and that's about the photographer's tracking and compositional skills.
You may get better answers on the Micro Four Thirds Forum.