If you ride on lit streets then you have all the background clutter of other lights and maybe can justify a hyper light by having to compete with this clutter. On the other hand, if you ride mainly in pitch black lanes then <snip>
In the lanes a bright front light can cause problems that do not exist with more feeble lights.
This.
I mentioned somewhere that I got out my
really feeble light one dark ride (for which read icba to swap over my dynamo hub) which was fine to see by in the pitch black ('cos my eyes adjust etc.) but the moment any other light appeared (car, porch light, floodlit farm/church, etc) then I was bedazzled to squinting sideways-ness to be able to see. In towns, my eyes adjusted to streetlights and car lights weren't a problem - it's the
contrast.
So what is to be done.
Lights to see by, cars, town - not required where there is street lighting - didn't there used to be some rule that said you didn't need headlights if the street lights were less than 30 yards apart? Up for debate.
Lights to see by, cars, unlit streets - need to be able to see for xxx seconds ahead, whatever is sufficient for that at 70mph and no brighter
Lights to see by, bikes, town - similar to car sidelights
Lights to see by, bikes, unlit streets - same response as for cars, though your top speed may be less than 70mph
Lights to be seen by - not clear whether they need to be brighter of dimmer than the lights to see by.
Better go and chew it over a bit more, it's got to beat going shopping.