Tom Blodgett wrote a concise and perceptive categorization of the tone and other characteristics of the "big three" clarinet makers: Buffet, Selmer and Yamaha. The context was a discussion of the rise of custom clarinet makers, with particular mention of Luis Rossi. He also cites Backun, and the rise of custom parts and the use of different woods. Tom did not mention Leblanc, so I'll wait for readers to fill in that gap. I tried a Leblanc or two briefly, and found their tone mellow and appealing, but not as interesting as Buffet.
An important point about tone: the player brings their own tone to whatever clarinet they play. The key is to find an instrument which is comfortable and allows you to sound like you.
Here is Tom's note-
Being a clarinetist, I feel I have insight to this specific line of questioning.
It is a swing of the pendulum, where in the early 1900s independent makers started getting bought up and the musical instrument industry began to standardize, centralize and mass produce, now there is another swing thanks to the void left by that conglomeration which is being filled by artisans such as Rossi who focus on quality rather than "other things".
There is also the effect of customization that most larger brands can't offer. Yes, the large companies offer several different product lines based on beginner, intermediate and advanced levels, and even several models in each category. But with the movement in customization, you can now get custom mouthpieces, ligatures, barrels, bells, reeds, and even custom boring and undercutting of tone holes, not to mention gold, silver, nickel, or even platinum plating on the keys. These all do effect the overall tone quality of an instrument, as well as tailor the setup to the individual in order to maximize a players capabilities (too bad many people alter their equipment instead of fixing their problems first).
As far as the difference in tones, I firmly believe that (unfortunately) there is no standard tone for the clarinet. Everyone is happy that the clarinet player just doesn't squeak. I personally think the big 3 makers - Buffet, Selmer, and Yamaha cater to different needs - Buffets have the best (sweetest) tone with the best key work (if you don't get a lemon) and are more for solo work. Selmers are the darkest and heaviest, their key work is different than the Buffet, but in no way negative. They are good for large orchestras. Yamaha has the best consistency instrument - if you've played one, you've played them all. In my mind, these make the best military and band applications, where there is much more uniformity in tone and intonation.
All that goes out the window once you start changing the stock pieces, and it started with mouthpieces and ligatures, then moved to barrels, then bells and bores, The final straw was Bakun who started (or re started...) using different types of wood other than grenadilla, such as rosewood, which has a much warmer, but less vibrant tone. That's also when makers like Rossi threw their hat in the ring, and we have come full circle to the 1700s when makers made individual instruments for individuals. The only diference is that the availability and variety of materials and the accuracy and speed of the machinery used.
In the end, the big 3 will most likely always be the top choice for factory instruments. There is room for custom makers, but the players and the public have to be able to accept them in order for them to survive.
Just my $.02