Bach 1½C vs Schilke M3
The Schilke M3 has a wider cup diameter, the Schilke M3 has a larger throat opening.
Cup Diameter
The Schilke M3 has a cup diameter of 17.07 mm / 0.6720 in compared to 17.00 mm / 0.6693 in on the Bach 1½C — a difference of 0.07 mm / 0.0028 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a medium cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
The Schilke M3 has a wider throat (3.86 mm / 0.1520 in vs 3.66 mm / 0.1441 in). A wider throat allows more air through, increasing volume and projection but reducing resistance.
Which is better?
Neither mouthpiece clearly dominates the other — the right choice depends on your embouchure, playing style, and the sound you're after. Try both if possible.