My ears tell me that many of the York style piston tubas don't really offer an increased amount of sound in any range in particular. High frequencies seem to be dampened, and I think players can get away with putting more energy through or in them without being called out, because of the fact that the high frequencies are dampened. Getting a deep wide sound out of a tuba can be gratifying and fun, but it also presents challenges in clarity. Admittedly, it's also a lot of fun to be able to blow the crap out of a tuba (as long as one is healthy and energetic enough to be able to do that) WITHOUT being called out by the music director.
Someone could point directly me and say "Look at the pot calling all the kettles black", but the reason I'm attracted to the particular large tuba that I recently chose (a non-York-like model that I have admired for quite a few years, but that I had no idea I'd ever be able to own) is due to the fact that somehow it manages to offer a wide deep sound PLUS clarity, and without me having to resort to using some shallow mouthpiece - or other type of trick, and without having to blow the crap out of it.
Were I studying music in Philadelphia quite a few decades ago, maybe only owned a wretched tuba, and my teacher offered me affordable terms on a great big York tuba, I would probably have taken them up on it - particularly when there were so few choices, very little importation, only trial and error bugle tapering technology, no internet, no woodwind/brasswind catalogs, and no tuba shindigs) but those medium large Conn instruments - such as the one that person's teacher ended up keeping and using, were probably more practical and more flexible, as far as application...
... and those silly stories about that person's teacher being too fat to play the York tuba are just as silly as the stories that person themselves only having one lung.