In general, the less-known a brand is, the lower the cost will be for their instruments. Naturally, the quality of instrument will be lower. Good makers of professional tuba sare usually considered to be Conn, King, Yamaha, Holton, and some more specialized. Jupiter is also making tubas, but I have not heard many great things about them, they especially have poor tone quality I hear.
In general, in looking for a tuba, there are certain things to consider: intonation, quality of tone, "feel", projection, and many others. These aspects vary from brand to brand and model to model even for just BBb instruments, and that is why we must be very careful in choosing the right instrument. The instrument that is right for me may not be the one that is right for you, so we must go down our own roads, trying things for ourselves.
On a related note, how do you know when to use a CC tuba or a BBb tuba? They are only a tone apart, so the feel and tone are similar... is it for fingering issues? Likewise with Eb and F... one or the other, which is for what?
P.S. My home practice instrument is some ancient no-name convertible 3/4 tuba that I found hidden in our instrument room at school. It has a few broken solder joints and very fluffy feel to it, but otherwise plays great. It was in a Conn case, so I think it is a Conn, but I've yet to see an unmarked Conn. The mouthpiece I found with it was also a Conn, and was of very percuilar shape. I use a Conn Helleberg (big surprise.)
The instruments we have at school are two Yamaha YBB 321 of the non-silver-plated variety. One is cruddy, the other is cruddier. My Conn(?) at home is ever cruddier. The better of the Yamahas is the one I use at concerts and band events (District band, Honors band, ect.)