I've only got the Abraxas neck pickup, in a Gibson The Paul SL (mahogany, no maple top) with a Rebel Yell in the bridge.
I chose it because Carlos Santana's distorted neck-pickup lead tone has always been one of my absolute favourite guitar sounds. I'm not a huge Santana fan, but I love that sound. The Abraxas neck really does nail it - fat, smooth, sweet and singing, with just a little bit of sparkle to stop it getting mushy. I haven't got a Mule to compare with, and my Stormy Monday's not fitted yet, but I suspect the Abraxas is a bit hotter and less vintage sounding.
From what I've read, the Abraxas bridge is also like a "Hot PAF" but a little bit smoother and warmer than, say, the Crawler, Emerald or VHII. I went for the RY because I like my bridge pickups to be quite bright and snarly, to contrast with the neck.