I lack the vocabulary, particularly with music and electric guitars, to describe in words what these pickups are all about.
So I'll make up my own.
Here's what a typical PAF sounds like to me at three positions - tone all the way to treble, tone half way back and tone all the way down:
Tone all the way to treble:
Chin ... Chin ... Chin ...
Tone at 5:
Kahg ... Kahg ... Kahg ...
Tone all the way down:
Blug ... Blug ... Blug ...
Here's what a 70's HB1 sounds like:
Tone all the way to treble:
Briiiing ... Briiiing ... Briiiing ...
Tone at 5:
Blaaang ... Blaaang ... Blaaang ...
Tone all the way down:
Grawng ... Grawng ... Grawng ...
You can't argue with science!
Anyway, I think that it's a mistake to think of the HB1 as merely brighter, because I like the full-fat jazz tones from them, and that's not really about the brightness.
I just think that it is more of a "full-spectrum" pickup. Lows to highs are all represented very well, iwth no dead spots that I've noticed. This is why you'll hear such tremendous diversity in style among HB1 players. From Grunge and Noise to electric fingerstyle. You can max out your amp and still hear the notes.