Bruno Tilz 214-D 5 vs Bruno Tilz 215-3 GS
The Bruno Tilz 215-3 GS has a wider cup diameter, the Bruno Tilz 215-3 GS has a larger throat opening.
Cup Diameter
The Bruno Tilz 215-3 GS has a cup diameter of 27.00 mm / 1.0630 in compared to 26.00 mm / 1.0236 in on the Bruno Tilz 214-D 5 — a difference of 1.00 mm / 0.0394 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 215-3 GS has a wider throat (6.80 mm / 0.2677 in vs 6.30 mm / 0.2480 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.