Bach 1½C vs Schilke 15Heavyweight
The Schilke 15Heavyweight has a wider cup diameter, the Bach 1½C has a larger throat opening.
Cup Diameter
The Schilke 15Heavyweight has a cup diameter of 17.12 mm / 0.6740 in compared to 17.00 mm / 0.6693 in on the Bach 1½C — a difference of 0.12 mm / 0.0047 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 Bach 1½C has a wider throat (3.66 mm / 0.1441 in vs 3.65 mm / 0.1437 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.