Bach 6½AL (large shank) vs Yamaha SL-45C2S
The Bach 6½AL (large shank) has a wider cup diameter, the Bach 6½AL (large shank) features a deeper cup, the Bach 6½AL (large shank) has a larger throat opening.
Cup Diameter
The Bach 6½AL (large shank) has a cup diameter of 25.40 mm / 1.0000 in compared to 24.26 mm / 0.9551 in on the Yamaha SL-45C2S — a difference of 1.14 mm / 0.0449 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Bach 6½AL (large shank) has a deep cup while the Yamaha SL-45C2S has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Bach 6½AL (large shank) has a wider throat (6.63 mm / 0.2610 in vs 5.85 mm / 0.2303 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.