Schilke 42 vs Yamaha SL-45C2S
The Yamaha SL-45C2S has a wider cup diameter, the Schilke 42 has a larger throat opening.
Cup Diameter
The Yamaha SL-45C2S has a cup diameter of 24.26 mm / 0.9551 in compared to 23.22 mm / 0.9142 in on the Schilke 42 — a difference of 1.04 mm / 0.0409 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 42 has a wider throat (5.95 mm / 0.2343 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.