I don't have any experience with the Metzelers, but just going by what I've read from this and other boards, both are good, the Z6 is probably the better handler, but I don't know if it wears better or worse than the Z4, but the Z6 is the replacement for the Z4, so if you go with Z4's, be sure they aren't old (by manufacturing date).
A friend runs the Avons in 120/180 sizes on his B12 and liked them well enough to buy a second set. They don't seem to last as long as my Michelin Pilot Roads though.
I'd stay away from the Mac100 though. They don't cup as bad as the 90's did, but they still cup. They've been replaced by the Pilot Roads, so like with the Z4, be sure to check dates on them.