Other than pictures, I've not laid eyes on the new 494.
I recently/finally played a 282.
Obviously (you know me...) there are SEVERAL things I would change, but the 282 (the one that I played) plays REMARKABLY well in-tune...not very much slide-pullin', particularly if someone is willing to play G-up-in-the-staff and low G (down below the staff) with 3rd valve.
Maybe (??) the 282 seems a bit "turbo-charged". Even though a (albeit large-@$$) 3/4, it's got quite a "carburetor" on it - featuring the same bore size as the 186 tubas. It's pretty easy to get really "bright" on a 282...maybe even easier with a 184...and (282) peaking out the decibel meter (in conjunction with the bright sound), as well.
The thing is that the JP 379B - Cerveny Arion copy (and no...This isn't an ad for a model that I sell...only noticing differences) has an even slightly larger bore and no larger of a bell, but the sound is noticeably more "covered" than with the Miraphone 282. ...and (again) I'm curious as to whether anyone has played a Miraphone 494.
Yeah...This probably looks like an old "vs." post from the early boob-net days...Maybe (??) that's just what it is...
EDIT: I also just discovered that Miraphone makes a model 1272, which is a front-action PISTON version of the 282.
These are all - very roughly - in the same size range and - very roughly - in the same valveset bore range:
Miraphone model 494:
' looks as if this could easily be hot-rodded to a 7-valve tuba and - with a bit more effort - an 8-valve tuba... ie. It seems to stay small for quite a ways, with considerable hesitation in the expansion of the bugle.

Miraphone 282:
282 requires quite a long pull on the #3 slide for good intonation, which causes it to nearly interfere with #1 slide manipulation, if desired. It also calls for a long main slide pull for A=440, which tells me that the best place for a 5th rotor would be (as with some piston tubas) past the LARGE side of the main slide - just before the dogleg...also with a bit of main slide ferrule-shortening. Assuming the #3 slide (issue previously mentioned) could be dropped down, that upper #4 cylindrical loop would double as a nice comfortable left hand rest, were it that it were also protected with a nickel "hand shield".

Miraphone 1272:
