Bach 8½A vs Yamaha CR-11E4S
The Yamaha CR-11E4S has a wider cup diameter, the Yamaha CR-11E4S has a larger throat opening.
Cup Diameter
The Yamaha CR-11E4S has a cup diameter of 16.46 mm / 0.6480 in compared to 16.10 mm / 0.6339 in on the Bach 8½A — a difference of 0.36 mm / 0.0142 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a very deep cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
The Yamaha CR-11E4S has a wider throat (4.20 mm / 0.1654 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.