ANY sim, sample set, whatever, is going to be a poor substitute for the real thing. The question is of DEGREE... I happen to think that of all the pianos in arrangers, the G70 is head and shoulders above the rest. But it in no way compares to a REAL piano.
So, when asking about organ Leslie sims, sure, you can reference back to the original, but once you accept that the real thing is completely impractical, it is simply a question of degree. So, once again, I ask you which you consider the 'best' sim available? After all, as an organ enthusiast AND retailer, you are in probably as good a position as anyone to give an informed opinion.
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An arranger is just a tool. What matters is what you build with it..!