Conn Connstellation 9BN vs Monette Cornet AP1-1 S13
The Monette Cornet AP1-1 S13 has a wider cup diameter.
Cup Diameter
The Monette Cornet AP1-1 S13 has a cup diameter of 17.00 mm / 0.6693 in compared to 15.88 mm / 0.6252 in on the Conn Connstellation 9BN — a difference of 1.12 mm / 0.0441 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a very deep cup depth, so the sound character from depth alone will be very similar.
Material
The Conn Connstellation 9BN is described as Silver-plated brass, and the Monette Cornet AP1-1 S13 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.