My very brief thoughts,
Mouthpieces are a very personal things, and we need to find what works for US personally. That being said, Mercer & Barker is doing amazing things. For wind band playing, I would look at the Brandon Jones pieces without a doubt. It's a hybrid of the Bowman and Schilke 51D. Absolutely amazing in feel and core sound produced. For brass band playing, I am very partial to the Wick mouthpieces. Namely the SMX line. Just my preferences though.
Ben Dawley
Music Director
Solo Euphonium, Five Lakes Metro Brass Band
Besson Prestige 2052 (Gold)
Shires Q41S (Medium Shank)