It has a whole lot more to do with the person playing the guitar, and how the modeled sounds interact with whatever effects and amplifiers that player uses. I have used both 1.9 and 2.0 at the gig. For the key sounds I rely upon in the Strat department, 2.0 did not work for me. I'm back at 1.9... when I'm not taking one of my real Strats to the gig. Sorry if this offends anyone; it is, however, MY opinion -- and I'm the one who is playing the guitar and counting on certain sounds to make ME happy so I in turn can make the audience happy. Most of them couldn't care less... but I do.
So, at a gig, while playing a Variax with v2.0 firmware, how many members of the audience are going to walk out and demand a refund because they prefer the sounds of the v1.9 firmware?