Kelly SCREAMER vs Yamaha TR-14B4
The Yamaha TR-14B4 has a wider cup diameter, the Yamaha TR-14B4 has a larger throat opening.
Cup Diameter
The Yamaha TR-14B4 has a cup diameter of 16.85 mm / 0.6634 in compared to 16.00 mm / 0.6299 in on the Kelly SCREAMER — a difference of 0.85 mm / 0.0335 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a shallow cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
The Yamaha TR-14B4 has a wider throat (3.65 mm / 0.1437 in vs 3.56 mm / 0.1402 in). A wider throat allows more air through, increasing volume and projection but reducing resistance.
Material
The Kelly SCREAMER is described as Lexan polycarbonate, and the Yamaha TR-14B4 as unspecified. Material affects mass, warmth, and how quickly the piece responds.
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.