We also chose trail 6 because it ran beside Biwataki waterfall. This waterful is very sacred and has a temple/shrine at the bottom. The waterfall is used for takigyo, waterfall meditation. You stand under the pounding water and pray/chant, usually for hours at a time! I've heard that monks even do it in the dead of winter when the water is freezing!
We will definitely be going back, we also plan to hike Mt. Mitake soon.