As a British brass band, I suspect your choice should be restricted to Besson sounding EEb tubas (4 valve compensating with the 4th valve operated by the left hand).  Personally, I would like to see much more progressive and divergent developments in brass bands but I can't believe those with influence will encourage this - quite the opposite.  In other words, the chance of Sousaphones, French Horns or trumpets being used when appropriate is not likely for another 10 years.  More relevantly, the expectations will continue towards Besson BBb and EEb sounding basses regardless of the fact that there are many other basses which are very nice instruments

There is nothing inherently contradictory in being traditionalist and progressive at the same time. If you want the valves, bore and wrap of a 3+1 comp, fine. I personally prefer that tone myself. But on a 4-valve comp, you still have the same intonation issues as with the first three valves of any tuba, conventional or comp. So why must the manufacturers insist on retaining the uncomfortable 3+1 arrangement, when Besson themselves, before going bankrupt, demonstrated it is possible to have 4-valve right hand in front comp tubas with the Phil Sheridan Eb and the 993 BBb? By putting the valves in a front arrangement you can wrap, especially, the first valve slide so it can be manipulated as necessary for minor intonation adjustments, especially on 12 combinations to keep them from being sharp.

i am very curious about the new york instruments! unfortunately i'haven't got the chance yet to play a york EEb tuba. but i tried a york Bb tuba some weeks ago. i was quite impressed of the instrument an his sound. also the whole manufacturing and valve speed was great!
(right now i play a yamaha EEb tuba i am very happy with, before i played Besson Bb tubas)

I have played a York Eb and it feels and plays like a sovereign. the "floating leadpipe" gives it an interesting feel, but i wonder how vulnerable it will be to leading edge knocks. I also wonder to what extent its rave reviews are due to the poor quality of sovereigns over the last 10 years.