Well, I don't know if 'fool' is quite the right term, but there's a radical difference for the listener between someone playing a guitar part idiomatically, and someone just playing their old piano licks or whatever...

And, to be fair, playing idiomatically is probably a hundred times more important than an accurate, multi-velocity split sound... whether the fret buzzes are in the right place or not. I think our audiences can pick up on a non-idiomatic performance far quicker than they can on the sound. Of course, once you have the idiomatic playing down cold, then the sound accuracy starts to become a bit more important. But, truth be known, if you can't give a pretty good impression of the instrument you are trying to emulate on what you already have, a more detailed set of samples isn't going to make you sound any better at all.