My old Besson is really starting to show its 35 years of accumulated abuse before I got it: solder joints deteriorating, red rot, leaking, etc. but I still love it for all those reasons in your post.
I'm even considering looking for another bell and bottom bow to rebuild it, because in spite of it being stuffy on low C and B nat, the tone is huge and the intonation, until recently as the leaks start to get worse, has been perfect. Mine does have its limitations in the low range in that regard, being a three-valve, so I may have to get something else for university community concert band to handle the low extreme registers we're getting, and to be a little smoother in tone and blow over the change in registers down low, as it does take about three lungs to keep a fortissimo going below open BBb. But for everything else where tuning is more important than a couple of stuffy notes, and the literature doesn't get extreme, it's still my favorite, especially with the Wick 1 mouthpiece designed for it.
But you're right: I chose a three-valve because the four-valve ergonomics are a nightmare. About the only persons I know that might be comfortable with it would have to be about 6' 6" and have a sleeve length of at least 35"! Besson was finally on the right track to fix it with a front-valve version introduced about a year or so before bankruptcy. I don't know the status of whether Buffet-Crampon are going to carry on with it or not. All the spinoffs and other manufacturers who make comps still make the 3+1 upright versions which just don't make sense anymore.
Also, even though the three-valve is theoretically perfect in its intonation all the way down, with only 123 B nat and low E nat being a hair sharp, but no sharper than 12 G and D on a conventional tuba (on a comp, you use 3 alone instead of 12 as it is in perfect tune and the comp loops take care of tuning up 23 and 1-3), the four valve is not. For any combination of 1, 2, and/or 3, you still have the same intonation compromises as you do with any non-comp, and you can't get to any slide to pull it, say for 12 G or D or 23 Gb or Db, because your left hand is doing double duty steadying the horn as well as working the 4th valve. It's only with the 4th valve and all the low range being in tune without pulling that a player realizes the benefit of a 4-valve comp.
With the front valve version, it's no different than any conventional 4 valve BBb, you can get to the slides as need be for 12 and 23 combinations, and still have the advantages of not having extreme pulls in the near pedal register.
Now, what was that carcass I recently saw on eBay....
