Kapusta

For street riding I don't use a helmet "light". More like a white blinky on the front (and a red blinky on the back) just to be seen at night.

As far as MTB.... If I plan to night ride, my setup consists of three cheap Chinese no-name lights. They "claim" to be something like 1,500 lumens each, but I doubt they are much over 1000, if that. I am really just guessing. I have two mounted on the bars and one on my helmet. So the short answer is that I have less on my helmet simply because it is only one light as opposed to two... but there is more to it.

For one, the lights on the bars use flood lenses, so it takes a lot more lumens to run them bright enough. I have one pointed down fairly close in front of my bike that I run on Low setting, and one pointed farther down the trail that I run on High (and turn off during climbs). On my helmet I use the spot lens, so it does not require as many lumens. I usually run it on Med or even Low sometimes.

Also, I don't like the light that comes from the helmet as much as from the bars. Because the light source is so close to my eyes, I can't see shadows as well, and everything kind of washes out. The light from the bars casts more shadow and I can see texture and features on the trail (and road) much more easily. The helmet has the obvious advantage that it can be pointed anywhere, so I do use it, but I don't want it too bright and washing everything out.

My MTB lights are kind of a pain to set up with all the external batteries and cords. If I am riding and planning to get back within a few hours before dark, and want a light just in case of emergency, I will just throw my cygolight in my backpack. It is not optimal for trail riding, but it will get me out of the woods just fine.

As far as blinding other people.... I try to remember to shut the helmet light off when we stop... or keep looking away from everyone.