The subject of mouthpieces is one fraught with misinformation, received wisdom (not always right). Every player is different, different physiology, physiognomy, lip size, teeth, etc. What works for one player may not work for another. Classical teachers seem to have a prejudice for large mouthpieces. Bobby Shew once said, "Play the smallest one you can get away with." Jon Faddis plays one more shallow than a blond. Depends on what you want to do too. I have a student who was struggling last year trying to get through a day of rehearsals, and the last one of the day he couldn't play at all. Turns out he was playing a 2C because his band director told him you have to play on nothing smaller than a 2C. Once he switched to a 5C he had no more endurance problems. When I was in grad school Byron Stripling told me I should play a larger piece-at the time I was playing a Schilke 14A4C. I went to my teacher, Barbara Butler, and said, Barbara, Byron says I should play a bigger mouthpiece, what do you think? (Byron played a 1, not a 1C a 1, but then again he was and still is the chairman of the Big Lip Committee.) Barbara said, do you like your mouthpiece? Yes. Do you like how it sounds? Yes. Does it do what you need it to do? Yes. Are you comfortable with it? Yes. Then tell Byron to go f*%k himself. I didn't (he was much larger than I was) but I ignored his mouthpiece advice after that.