The theory that the Boehm system clarinet can cover all bases is a relatively old one. Starting after the instrument was "perfected" in the 1800s, there was a strong bias against other pitches of sopranos, and a tendency to rely on the Bb instrument to "do it all". With the addition of one key, it covers the range of the A horn, and the others (C and D) are already within the compass of the horn. Presto - a three or four horn collection brought down to one.
As anyone who has to schlepp a two or three horn case around the block knows, that's a big reduction, not only in weight but also in monetary investment. While it does get a bit sticky in extreme keys, transposition so you can play it all on one horn is quite possible.
(The so-called "full Boehm" clarinet was developed (in part) because some of those sticky transitions in extreme keys are better enabled. One of the "improvements" (the LH Eb/Ab lever) has made its way in to the mainstream over the past twenty years, but the others (most notably the articulated G#/C#) make a world of difference.)
I tend to stick with the full Boehm Bb for almost all of my clarinet playing. Last fall marked the first time that I had used its sister in the heavy double case for anything but a periodic practice session, and even then I could have handled the part on the Bb had I wanted to.
Having started out on a bass clarinet pitched in A, I am well aware of the utility of the A clarinets. But, transposition only cost you more practice time - an A clarinet costs a lot, lot more.
As for Yamaha equipment, I'm a fan of their motorcycles, saxophones (I have a YBS-62, bought to replace my long-departed Selmer baritone, and would not go back for all of the butter in Wisconsin) and miscellaneous musical equipment (I have a wonderful Yamaha mixer board - a great piece of equipment and very reasonable in price for what it does, and a Yamaha "keyboard" that all of my pianist love to pieces).
However, I've never liked any of the Yamaha clarinets (soprano or bass) that I have tested or played. Mind you, I have not done a comprehensive survey of their clarinets from top to bottom. But, my experience to date leads me to believe that their clarinets (like those from Leblanc (too chunky in the hands) and Buffet (so frail feeling that I'm scared that I'm going to crush them)), are just not for me.