Miraphone 186 (4v, gold brass)
Nice tuba, I haven't tried many 186's, but I did like this one better than most others I've tried. Great response and nice classic "this is what a tuba sounds like" sound. Just stupidly easy to play, too. A little smaller than I'm used to, so I was probably overblowing a little bit at the top end.
Miraphone 188 (gold brass)
Holy crap! What a tuba! This was the tuba that made me run home, count the penny jar, look in the couch cushions, etc...

Miraphone 188 (yellow brass)
Still a nice tuba, but for me a totally different animal from the gold brass 188. No complaints about it, but not my favorite either.
Dillon CC tuba
I didn't spend much time on this, just a quick honk. It played decently and sounded pretty good. Clearly, I liked the Miraphone 188, and I played that one first. So for me, I knew it was NOT a Miraphone, and was probably more aware of the side-by-side differences. But, being so much cheaper, it seemed like a pretty good deal for the $$.
Besson 995
This was a really nice tuba. Great response, big fat American/York-ish sound, and really easy to play. For me, it was pretty heavy (physical weight) and the valves just didn't seem to "fit" my hand very well. That was enough for me to cross that tuba off the list... but I did like the way it played!
Miraphone 291 (Bruckner)
This is a fantastic tuba. I owned a 1291 for several years, and this really did feel like a rotary version of the 1291. What struck me more than anything else was the incredibly small amount of effort needed to make this thing "go." This thing responds almost instantly, and felt very "live" and resonant. Would be curious to hear one of these from a distance in a hall... Sound was just awesome, intonation was great, and it was just a ton of fun to play. A real close toss-up between this and the GB 188 for what was my favorite CC tuba. The 188 took just a little more effort to play, but I liked the sound of the 188 better (personal preference!)
Also tried a few F tubas, and truly loved the gold brass Miraphone Firebird they had. It was everything I liked about the 188 but in an F tuba. Oh, and the low C was great!
Just my opinions, if anyone is interested to read them!
