Bruno Tilz 231-C 4 vs Bruno Tilz 310-M 0
The Bruno Tilz 310-M 0 has a wider cup diameter, the Bruno Tilz 310-M 0 has a larger throat opening.
Cup Diameter
The Bruno Tilz 310-M 0 has a cup diameter of 33.70 mm / 1.3268 in compared to 33.00 mm / 1.2992 in on the Bruno Tilz 231-C 4 — a difference of 0.70 mm / 0.0276 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 Bruno Tilz 310-M 0 has a wider throat (8.30 mm / 0.3268 in vs 8.20 mm / 0.3228 in). A wider throat allows more air through, increasing volume and projection but reducing resistance.
Which is better?
Both mouthpieces are categorized as "Catalog" — the physical dimensions above will determine which suits your embouchure and playing style better.