I have NI B4 mkII and it makes me droll just holding down the keys! I happened to pass through a music shop a few weeks ago and they had a full Hammond organ with pedals and a Lesie speaker and it sounded great no doubt. I think the B4 comes close enough though in the studio.
I view it as this: You can’t compare a real instrument like Hammond/Leslie or Strat/Marshall to a simulated one, but you can compare a micked up organ+amp or guitar+amp coming through the wall in to the studio monitors to a sim instrument also coming through the studio monitors. And in 2013 it’s close enough to say that in the studio it makes no sense to drag the real poop around just for the sake of it. If you have some special set up you rely on for whatever reason of course you should use your hardware, but most of the time it’s not significantly better.
The sims take no space and you can save presets of hundreds of combinations. Hardware can’t. Hardware can WAIL and SCARE SMALL ANIMALS, TICKLE YOUR EARS, ROCK YOUR SOCKS OFF and SOUNDS DANGEROUS in the real world. That’s their place!!! 
Where were we? Oh, the B4! Great plugin!
Get on if you can … Native Instruments discontinued it a few years ago, though!!! 
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Same goes for the Mini Moog, of course!