Denis Wick 4N vs Marcinkiewicz CH EF 21J. Cox
The Denis Wick 4N has a wider cup diameter, the Denis Wick 4N has a larger throat opening.
Cup Diameter
The Denis Wick 4N has a cup diameter of 18.00 mm / 0.7087 in compared to 17.48 mm / 0.6882 in on the Marcinkiewicz CH EF 21J. Cox — a difference of 0.52 mm / 0.0205 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 4N has a wider throat (4.70 mm / 0.1850 in vs 4.57 mm / 0.1799 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.