First things first - the Marshall ShredMaster is not only a metal head pedal. It may use silicon diodes to shunt the signal to ground, for sym. hard clipping, but the contour control - offering middle boost and cut sounds - gives a wide range of usable sounds: from bluesy crunch to scooped rock. This one has a new switch and the rubber pad on the bottom is missing, the battery door however is still there. - (€100) The Marshall BluesBreaker uses silicon diodes in series with a resistor, in the op-amp feedback path for very soft clipping. It's therefore a very subtle overdrive pedal, with a warm sound. John Mayer likes the way it colours a single coil. I do like it on my "The Paul"s neck pickup the best. Really nice pedal - not as mid heavy as an OD-1 and slightly more transparent but in the same category quality wise. The Marshall DriveMaster uses LEDs shunting to ground for symmetrical soft clipping. So technically it's an overdrive pedal - but just like the Distortion+ (which technically is an overdrive as well) it's very capable of distortionesque tones. The EQ section is superb and especially the Middle and Treble controls are quite interactive. This is one of my favourites for singing solos and power chord rhythms.