Originally Posted by rowuk

WHOAH!!!!!!!!!!!!!!!!
Slow down a bit!

You essentially have the 2 extremes of mouthpiece size and claim the difference is range and endurance. Without hearing and seeing you play, it is hard to know exactly what the deal is, but I'll bet it has NOTHING to do with the size of your mouthpiece. The factors that you mention are usually SYMPTOMS of something much more basic - a weak foundation - your breathing not being together. Basically, if your breath support is adequate, what changes the most with mouthpieces is your tone color. Range and endurance does not change appreciably - at least not on the repertory that you mentioned.

If your breathing is not together, the smaller mouthpiece can compensate by lowering the requirements.

This was just to put the differences into perspective.

A deeper cup does offer a darker sound. Without ever having seen and heard you play, I don't know if a 10B is the answer. The deeper cup will also require more breath support. There is a philosophy among some fine players that one should always use the smallest mouthpiece that you can get away with. I think that concept only works with professional players. Amateurs benefit greatly from a "slightly" larger mouthpiece. There is simply more flexibility when the practice time is erratic.

It would interest me to hear what your experience with a 7C would be. That is a bit bigger, has a much more substantial tone, but not the requirements of a 1 1/2C. In any case, additional breathing exercizes will help most!