Marcinkiewicz 3FLD vs Schilke 20F
The Schilke 20F has a wider cup diameter, the Marcinkiewicz 3FLD has a larger throat opening.
Cup Diameter
The Schilke 20F has a cup diameter of 17.78 mm / 0.7000 in compared to 17.25 mm / 0.6791 in on the Marcinkiewicz 3FLD — a difference of 0.53 mm / 0.0209 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 Marcinkiewicz 3FLD has a wider throat (4.32 mm / 0.1701 in vs 3.86 mm / 0.1520 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.