I have Mules, VHII's, Abraxas, Riff Raff, Stormy Monday, Emerald and just ordered a set of Black Dogs. I love classic rock and blues, so here is my feeling.
Stormy Monday - great neck pickup for the cleaner end of the blues rock stuff (Peter Green, Paul Kossoff)
Mule - Classic PAF, think Crossroads, Mr Big, Black Magic Woman (the original version)
Riff Raff - Brighter and hotter PAF sound - AC/DC sound really
VHII - more bottom end - thicker PAF sound
Abraxas - Hot PAF - think the Santana version of Black Magic Woman
Emerald - Lots of harmonics, I like this in the bridge with the mule in the neck. Could be bright with the wrong woods (same with the Riff-Raff).
So I don't know if this helps you. I have Riff-Raff (A5) with Stormy Monday (A4) for blues and original classic rock, Emerald/Mule (A5/A4) for more rock things and Abraxas for sustaining leads. My VHII's are in a PRS and this is a really versitile set. I am looking forward to hearing the Black Dogs. Another set that is interesting is a Mule Bridge and VHII neck (I know that sounds the wrong way around, but Tim said with the A5/A4 magnets it could work really well.
The A5/A4 give almost the out of phase shimmer that Peter Green used to get when you use both pickups.