I much prefer to wait until it's dry, but if it rains while I'm out there's not much one can do about it. Since being hit despite conditions really being in my favour, I am even less willing than before to share the road with the inattentive troglodytes who leech out of the woodwork when the rain falls. That's putting it mildly; I'd probably get banned from the forum if I wrote what I really think!
By the way, that bit about the disc brake pads getting ripped to shreds is really interesting, 'cos the general theory is that they are less susceptible to dirt because they're not picking up the muck off the rims.
Just ride the bloody thing and enjoy yourself!