(FOR ME - having worked through it with both,) it's remarkably easier with a 5-valve BB-flat tuba, than with a 5-valve C tuba.
The low pitches just speak more easily (less cylindrical tubing) and - well - the button-mashing is simpler, which allows the brain to think more about the "ominous" (musical) effects, rather than concentrating so very much on achieving the technical.
Just as one example...
The opening double-low E-flat (though not choice #1 of valve combinations) is played with 5-1-3 (#1 pulled out to the end, and I have installed a stop rod - see other threads) and the smooth movement to the E-natural occurs by dropping valve #1 and adding valve #2 (probably one of the smoothest "slurs" on a brass instrument) while (for spot-on intonation) letting the #1 slide in a bit. ...OK...this (with the slide movement, and the alternate for double-low E-flat) may seem somewhat complicated (ie. the opposite of what I'm claiming), but it's really easy to grasp cognitively, and - the execution of it is so very "it-plays-itself"-like.
(By now,) having gone through tons of standard orchestral literature on this new-to-me instrument with a - de facto - new-to-me length, playing a quite a bit of German "contrabass" literature on their (actually: required) instrument (BB-flat) is pretty eye-opening, and - working hard to execute those passages on a 5-valve C instrument, all these years - sort of makes me think of all the American trumpet players who work so very hard to play the opening to Mahler 5 on their C trumpets (with both intonation issues and wonky back-side-of-the-instrument issues).
My eyes were finally opened (after so many years of playing the tuba) as to what was obviously the instrument owned by the first tuba player to ever perform Scheherazade; just a glance through the entire part shows that the part is written barely within the range of a 3-valve E-flat tuba (though I wouldn't choose to use such an instrument to play that particular piece) - thus the wonky "octave jump" in the opening statement of the motif, but quite a few composers of the past apparently wrote their parts TO the instruments which would be playing them, rather than "what sounds cool when played back by the midi devices set up in their (otherwise would have been) guestrooms or children's rooms in their homes".
oh yeah..."the Ride" - as well as "Fountains" and "Metamorphosis": also easier (and ALSO easier to TUNE), once the button-mashing has become second nature.
re: bar 2671...I believe that should be quite loud, but (unlike a couple of "check THIS out" youtube videos) not so loud that the nature of the sound of the instrument is drastically changed, as Wagner ALREADY placed the loudest portion of the passage in the most resonant range of the instrument (ie. Allow the passage itself to do the heavy lifting)...but that's just one person's (my) interpretation...
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