Interesting thread.
I have to disagree with some of the opinions stated in so far, though, and offer a different perspective. The majority of playing I do these days is with community Orchestras and the rare paying Orchestra, plus quintet work. I can count on one hand the number of Band gigs I have done in the last 5 years.
Orchestral playing is about making as "characteristic" of a "tuba" sound as you possibly can, IMO. Sometimes the parts call for larger instruments and something the parts call for smaller instruments. But it is always a tuba part, written by the composer because he wants a tuba sound to voice the part. It's a challenge in an orchestra to have good intonation with a disinterested bass section or pretty much any 2nd bassonist, nevermind the axe murder playing bass bone.
Band playing is also about making a very characteristic sound as well, but there are times when you are playing parts that were originally written for String Bass or Contrabassoon. There are times when you play String Bass, Bari Sax, or Contrabass Clarinet cues (due to lack of instrumentation). The range of the types of sounds I have to have to "bring with me" for a band gig is broader and depending on the rep can be a very welcome challenge. Intonation is a challenge here because of the multiple tubas (usually) plus Euphoniums, Bari Sax, Bassoons, etc.
I am of the opinion, and the approach, that when I am playing a String Bass cue (or part) I try to make my sound more like that of a String Bass, and when I am playing (what would be) a String Bass part in an orchestral transcription for band I approach that differently as well. I guess I hear a different sound in my head and try and portray that sound as part of the performance. I use different mouthpieces, and I'll start/end notes differently, unless it's a Bari Sax cue in whcih case I play as ugly and out-of-tune as possible.

I also find that playing in an orchestra allows me more of a chance to be more expressive in my playing. Sometimes it's hard to be expressive when you're one of six tubas. It's still a challenge but I think they are quite different in nature and I use very different approaches.
Rob
Rob. Just Rob.