Bach 5V vs Marcinkiewicz 14S
The Marcinkiewicz 14S has a wider cup diameter, the Bach 5V has a larger throat opening.
Cup Diameter
The Marcinkiewicz 14S has a cup diameter of 16.31 mm / 0.6421 in compared to 16.25 mm / 0.6398 in on the Bach 5V — a difference of 0.06 mm / 0.0024 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 Bach 5V has a wider throat (4.09 mm / 0.1610 in vs 3.73 mm / 0.1469 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.