I've tried damn near every moderate to high gain Duncan pickup out there. Not many that I gel with but here's my take on some mentioned above:
Distortion: Probably my favorite of the classic bunch. Tight, Lots of upper mid cut, sizzly highs, very hot. Good alll around rock and metal pickup
JB: I love the voicing of the JB, even the mids that most seem to dislike, but the low end mush and lack of clarity turn me off every time. Great pickup on a plexi circuit though
Custom Custom: Too dark, compressed and mushy for my tastes. I'm just not generally a fan of alnico II mags though
Custom 5: Somewhat reminds me of a Gibson 498t, but without the grainy, angry character. Been a while since I've owned this pickup though
Custom: Similar to the custom 5, but tighter and brighter. Just kind of bland to my ears
Custom/Hybrid: same as above, but even more bland. I only had this in one guitar that I wasn't in love with, so take this with a grain of salt. People love this one
Other Duncan pickups I've tried:
Alternative 8: This is a LOUD pickup, good lord. On a clean channel, I remember this thing for some reason being way louder than the JB it replaced. Very unique sounding pickup, but I remember it had too much of a cocked wah mid sound going on and just didn't sit right with me over time.
Full Shred: A great all around pickup. I dig this one for lower tunings, especially in bright guitar. Clear, stiff, and bright. Unforgiving if you suck (which I do) but definitely makes you play harder and focus on what you're doing. One of my favorite Duncans
59 Bridge: I actually loved this one. Tight and percussive, more clarity and snarl than the customs. I would own this one again, no questions
Black Winter: Like the Distortion but a little hotter, brighter, and a little bit more grain. I really like this pickup, and currently have it in my LP Classic
Omega: Definitely a more modern sounding pickup, but tightness and clarity for days. Mids are nice as well. I have this in an LP studio and it's a tone monster for all things metal.