Schilke 10A4 vs Schilke 13A4a
The Schilke 13A4a has a wider cup diameter, the Schilke 10A4 features a deeper cup.
Cup Diameter
The Schilke 13A4a has a cup diameter of 16.76 mm / 0.6598 in compared to 16.43 mm / 0.6469 in on the Schilke 10A4 — a difference of 0.33 mm / 0.0130 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Schilke 10A4 has a medium cup while the Schilke 13A4a has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
Throat diameters are essentially identical at 3.66 mm / 0.1441 in, so resistance feel will be comparable.
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.