Bach 1½C vs Stork CM3
The Bach 1½C has a wider cup diameter.
Cup Diameter
The Bach 1½C has a cup diameter of 17.00 mm / 0.6693 in compared to 16.30 mm / 0.6417 in on the Stork CM3 — 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 medium cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
Throat diameters are essentially identical at 3.66 mm / 0.1441 in, so resistance feel will be comparable.
Finish
The Bach 1½C is listed as unspecified, and the Stork CM3 as Silver plate. Finish mainly changes lip feel, tarnish resistance, and appearance rather than cup geometry.
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.