Use these on the road bike I ride in the rain. Bought them to replace metal pads that squealed like crazy. These are quieter, but they still squeal. I don't know that it's the pad's fault though, I think maybe the rotor Shimano uses for their Ultegra set just might be noisy in the rain. In any case, it is an improvement.
I am still on my original pair of these disc pads. They are very, very easy to remove, inspect, clean andor sand if necessary - perhaps a bit easier to service than rim brake pads due to access. But that is open to debate. Cooling fins are not necessary for flatland use. I cannot comment on effectiveness for long hill or mountain descents.
Resin or metal for road? Resin is the answer - quiet, smooth, easy to modulate. Shimano quality. Mine last about 4-5,000 km on a pretty tough commute cycle. Great in hot or cold, sun or rain.