I recently put a HP II in Thomas Organ Cry Baby, & I like it. I had a HP I in there for years, & I thought it used to sound good with a tube preamp & Marshall 10 years ago. Over the years, I switched to pedals & Fender amps, & it didn't seem to sound as good.
Years go by, I try changing caps, resistors, & fiddle with values to make it sound "better", but it never did. Too "quacky" & "on-off" as opposed to full souning with a smooth transition. This was especially noticable with dirt & fuzz pedals. Granted, the pot could have been wearing out, but wasn't really scratchy. I put the wah away & built a new pedalboard without it.
A few months later, I started getting into Philip Sayce, & was wanting to use the wah again, but it sounded so bad. I changed the pot, & it's much better. Still not perfect (I don't know if there is such a thing), but, much, much better than before. It's a pleasure to play it again, & it works well with all my dirt & fuzz pedals. That wah doesn't have as much of a pedal travel as a Vox, but it still does the job.
But, without trying a brand new HP I & comparing it with the HP II, I can't really say how different they are. I only know that the new HP II sounds better to me than my older HP I.
For reference, the wah sounds I that like are SRV "Say What"; Hendrix "Still Raining, Still Dreaming" There are many more examples, but those two pop into my head.