Bruno Tilz 310-M 20 vs Marcinkiewicz ETU1J. Self
The Marcinkiewicz ETU1J. Self has a wider cup diameter, the Bruno Tilz 310-M 20 has a larger throat opening.
Cup Diameter
The Marcinkiewicz ETU1J. Self has a cup diameter of 33.15 mm / 1.3051 in compared to 33.00 mm / 1.2992 in on the Bruno Tilz 310-M 20 — a difference of 0.15 mm / 0.0059 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 Bruno Tilz 310-M 20 has a wider throat (8.30 mm / 0.3268 in vs 8.03 mm / 0.3161 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.