(My emphasis.) That's an unusual sonic term. Could you elaborate?
Okay, stiff/tight as opposed to bouncy/loose...
The PB with stock A5 has a very well-defined attack and a pretty quick stop at the end of a note.
A2 pickups generally tend to give a gentler, less aggressive attack and a less abrupt stop.
Most apparent when playing palm-muted with gain: players who chug a lot tend to prefer tighter pickups.
Detail also enters into the equation. Tight pickups render a lot of detail in the initial transients, I think.
That accuracy makes them less tolerant of imprecise playing; every tiny flaw becomes more apparent.
Looser pickups aren't as focused, and provide a little more "give" at the beginning and ending of the note.
They tend to smooth out minor inconsistencies and that makes them more forgiving for less clinical players.
The same way a soft-focus filter can gloss over blemishes in a photo.
Perpetual Burn is a great choice for precision players, maybe not as ideal for the less precise among us.
At least in its stock form...
Just opinion based on my own musings and experience.
Don't have any science to back this up.
But I'd argue it over a beer.
~
When it comes to broader questions of feel, that's hard to describe in terms specific enough to be meaningful.
I do find some pickups can make the strings actually feel less lively to me - a bit stiffer, almost like a different guitar.
Others seem to have a more elastic character - the strings feel a little springier, particularly under my picking hand.
A little less flat and a little more responsive, that's what I mean by bouncy.
I know that doesn't really tell you much but that's the way I think of it.
Changes in feel beyond output and EQ can be pretty subtle, especially since output & EQ affect the feel as well.
But I think further differences are perceptible - on a guitar I know well, through a familiar amp, at volume.
Damn, I miss playing at volume.