As someone encountering cyclists coming from the other direction at night in the streets, I detest the helmet lights there, as they usually blind me and require precautions to pass the other person safely. Of course, lights mounted on the bike can also be poorly aimed, but that is less common with them.
I'm mostly in the woods but your situations are interesting. in my experience, in my area, (when riding on a 2-way road) a helmet light isn't any brighter than a car headlight. a biker is further away from you because they would be on the shoulder across 2 lanes of traffic, traveling in the same direction as cars. maybe I'm not understanding your situation