Bach 8½A vs Denis Wick 4
The Denis Wick 4 has a wider cup diameter, the Denis Wick 4 has a larger throat opening.
Cup Diameter
The Denis Wick 4 has a cup diameter of 16.40 mm / 0.6457 in compared to 16.10 mm / 0.6339 in on the Bach 8½A — a difference of 0.30 mm / 0.0118 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 Denis Wick 4 has a wider throat (4.58 mm / 0.1803 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.