I tested various (ebay) cheap brake pads in the last 2 years, all were Magura MT's, either the small, 4-piston ones, or the 2 pistons (I ride the MT-trail model).
The best I've found (4-pistons models) so far were the gold semi-metallic, sold through Bikein e-seller. They proved to be silent, offered great power and modulation. They lasted the whole season (45km vertical climbing/descending in total, trail riding), but they wore down my rotor (front) to 1.77 mm (from 2.0mm) during that period of time. Some could say ... what you save on pads, you pay on rotors.
Also, I tested a 2 piston-model pad set, this one fully metallic (black one). Unfortunately, they stayed noisy (high pitch metallic noise), and glazed after a few rides. The pad compound is very hard (difficult to sand off the glazed surface). I ditched them.
Next test are going to be the ceramic compound (red one).
This said, I know Magura (and probably Shimano), advice against any metallic content in the pads, since they conduct heat and may bring the oil to boiling point. If I were to live on the West Coast, I'd probably stay away from anything but resin pads, but my riding area is quite flat compare to Colorado/BC.