Can't give hard numbers, but I installed this bulb based on Bare's recommendation after he assured me that the brake light IS quite a bit brighter than the park light - I agree that it is brighter, I use it, and I don't feel it compromises my safety. He rode behind this bulb quite a bit when he and Jack were riding their RE's together.
I don't know why there'd be a difference between bikes; maybe it's just individual perception? I don't have time today, but when I can, I'll try to shoot a video of the bulb "in action".