I used to have a Marshallhead, right now I use a Black Dog and Detroiter in my two LPs.
I will probably at some point in time own another set of Marshallheads. All three are in the same ball park, hot PAF-style around 9.3k.
Marshallhead - the most clear pickup I've ever used. It is fairly bright so best in a darker guitar, it really cuts. Has a bit of scooped character, not a lot of mids going on unless you bump them up on your amp. Very uncompressed, notes just jump right out. Fantastic note bloom on solos. Takes gain really well. The neck pickup is also the best neck pickup I've ever played. I almost never play neck pickups, as they are usually too low gain and muddy, but this one smokes, a lot of cut while still retaining the PAF character.
The only reason I don't have it anymore is at the time I only had one LP and it was too bright for it and I wanted a bit more mid grind. I should have held on to them.
Black Dog - uber-thick. If you have a plinky sounding guitar on top, this will thicken it right up and round off the highs. As per its description from BKP, notes have a lot of "weight" to them. It is very growly, grunty, clear, but lots of mid grind. Excels at both low gain and high gain. If you listen to all the high gain clips on the BKP site, the Black Dog actually sounds one of the best. Will put a smile on your face when you try it. Very unique sound. Kills at stoner/doom stuff, but equally at home playing Led Zep and blues.
Detroiter - Another one of those pickups that will put a smile only your face when you install them and hit your first chord. The hottest of the three, although I think it's more because it has a lot of high-mid nastiness. Many say it sounds like it has 10% P90 in its DNA. Very clear and 3D sounding, although I think it gums up a bit in the high mids, not as fluid for solos as the other two, a bit more dry. Not as much bass as the other two. A lot of snarl, with low gain its 70's Aerosmith, at high-gain its 80's thrash heaven. Guitarist from Overkill has used it on the last couple of albums.
Anyway, would love to get a Marshallhead set again, as my LP with the Detroiters is a bit on the dark side.
Wolfe is also a great guy. He hand delivered my pickup to me when I was in Seattle on a business trip.