The debate on bright, or not bright is as old as lights on bikes and will continue as long as there are two bikers alive on earth. In the end, if you read a bit about inattentional blindness, you will realise that the brightness of the light is nowhere near as important as those who believe in riding on bright seem to think it is. What is very important is for you to be different to the surrounding patterns and this is where the two extra spotlights, yellow / amber headlight, etc. excel.
Personally, I prefer dim purely because that leaves me with the flasher option.