Bach 1B vs Marcinkiewicz 1 1/4C (Endorsee)
The Marcinkiewicz 1 1/4C (Endorsee) has a wider cup diameter, the Marcinkiewicz 1 1/4C (Endorsee) has a larger throat opening.
Cup Diameter
The Marcinkiewicz 1 1/4C (Endorsee) has a cup diameter of 17.45 mm / 0.6870 in compared to 17.00 mm / 0.6693 in on the Bach 1B — a difference of 0.45 mm / 0.0177 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a deep cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
The Marcinkiewicz 1 1/4C (Endorsee) has a wider throat (3.73 mm / 0.1469 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.