Here is a fairly informative artical on brake pads. For trucks, ceramic or semi metallic are the only two realistic choices. Out of those 2, the cheaper semi metallic is fine and is the most common. The use of the coach is a big factor for example, if you plan to be traveling around the country on a regular basis towing a vehicle and running through the mountains, ceramic may offer some advantages.
we don't do lots of traveling, a couple of trips a year at 1500-2000 each. I read an article that semi-metallic stoop better with less pedal pressure, I have ceramic now but when they get hot they squeal and that's annoying for me and for those next to me with their windows down :-\
I prefer Semi Metallic on a heavier vehicle.
Ceramic are good for cars and mid size vehicles, but don't have enough bite to stop a heavy vehicle without a lot of pedal pressure.
Semi metallic operate with friction, Ceramic operate with adhesion.
I put Semi Metallic on my F350 that tows my 24' travel trailer and they stop nicely without having to stand on the pedal!