IMHO calipers.
If you have a good frontwheel stand it is probnably better engineering to pull the wheel (and not disturb the delicate bits) but unless you lie on the floor (with a d_a_m_n good torch) you can see and clean the piston & caliper assembly easier if it is off.
Jon
[ This message was edited by: lcjohnny on 2006-09-04 17:39 ]
True but I still like using the old toothbrushes to get the crud off the piston sides. Hoping to reduce the damage to the seals when I push them back in behind thick new pads.
And they have to come off as I haven't found a brush curvy enough to clean a 4 piston caliper while it is still on the bike.