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.
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.
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.