I have the 58/15s in my McCarty, and had the 57/08s in other PRSes and in my McCarty Singlecut. I haven't tried swapping them, and won't, because I'm not that pickup-swapping dude, but...
I really like both pickups a lot. Both are great at what they do, IMHO.
But I don't hear 57/08s or 59/09s in the 58/15s. I hear a more open sounding pickup in the 58/15, one that's closer to the open high end of a P-90 but without the noise, and with a richer midrange.
Also...my 85/15 in the CU24 is a hotter pickup than the 58/15 in my McCarty, and it's every bit as good a pickup as the 58/15, though obviously in the CU24 it's different anyway.
I think PRS is making seriously great pickups these days.