My band mate borrowed a QC for 3 or 4 gigs where we needed to fly.
In the studio, at high volume, he made it sound identical to his boogie MKII. At least that's what we felt. Impressive. We couldn't tell the difference (and that's a lot to say in his case, not in mine though).
We flight to the UK, to Barcelona... He also flight to Madrid as a guest guitarist in a big event.
Now he's going back to the amp. The feelings are: the QC is great. It's maybe the only option (well, any good digital modeller, I mean) if you can't carry your amp and still want to keep your tone more or less under control. BUT, if you want the amp experience in the stage, digital is still not there. He missed the response and the air of the amp behind him, which are reasons enough to think it's still worth to carry his amp and a big pedalboards over the comfort of just a little box. He didn't either like the response of the QC when stacking some boosts into de capture... Which he does live if he feels like it... And the amp just eats everything, while the QC can even start to squeal.
Not too much of a difference. He still thinks the QC is a life saver... But he's not buying one...
Regarding the audience... No, they're not going to tell the difference. It just sounds fantastic if the sound tech guy is not stupid.