M-Series: reminiscent of a mini-humbucker look, closer inspection reveals Ms are like nothing else sound is unequaled, huge single coil tone (think SRV without tuning down or changing to bigger strings). Ms trade thin, effervescent shimmer for single coil might. If you have been on the search for a fatter single coil tone, without having to resort the tighter focus of a humbucker, this is your magnificent answer (hum canceling, of course).
M1: Huge and fat, hum-free single coil tone for neck and middle positions
M2: For balanced bridge application with M1 in neck and middle
M3: Hotter bridge position, for a little more saturation when you almost want a humbucker, but not quite