Not sure really, as I've never liked bridge pickups for proper clean sounds, which I never actually play with anyway. So I can't really answer your question properly... but the Pig 90 seems a lot more compressed than the MQ, or less earthy as you put it. It's definitely not as compressed sounding as the Mules though, which sound quite flat/stale in comparison. YMMV though, as my amp (Laney GH50L) seems to be quite a dry and "stiff" amp, which seems to favour singlecoil-style pickups, humbuckers unless high output always seem to sound and feel a bit stiff or something through it.
As always it's probably best to email Tim :)