I played horn from age 10 until age 22, and after a couple of years off I'm starting to play again. I was always pretty mediocre, so I was content to use my elementary-school Holton MDC mouthpiece the entire time. I see from this chart that I've been using one of the smallest available mouthpiece sizes. Are there any reasons I should consider switching to a larger mouthpiece? In general, what do larger mouthpieces do better and what do smaller mouthpieces do better?
(If it's relevant, I usually play wind ensemble music on an F/B♭ double horn.)