This topic of comparison has come up before. Some folks have tested examples and come to strong conclusions that I do not agree with.
One guy's conclusion was that the PPC-9 was more accurate. I am not calling that guy a liar, but I am saying that what I believe he found was two particular examples and he was able to come to a conclusion about those two examples. All well and good, but ludicrous to suggest that it's the answer.
I have posited that anyone who owns at least one example of each has taken them apart to find that the top half is barely different across these models and it's not a correct factual scientific conclusion to claim one model is "more accurate" than another model by testing a single example of two models -- especially when the two models in question are basically using the same top end.
I would think that if you could source FIVE examples of each model and all running the same ammunition, you might find yourself with ten guns that all rank somewhere between 1 and 10 and it's doubtful that one model would show itself as significantly more accurate than another.
Furthermore
If you then took that same group of ten pistols and changed the control ammo, I believe your 1 to 10 ranking would also likely change, and you would again be likely to come to the same conclusion that no model lands heavier in the top 5 than the other model.
I think the question is interesting enough but I would be quite stubborn to be convinced that someone has a real answer backed by scientific methods.
This question would be far more compelling if you wanted to pit a S&W Performance Center pistol against the best that Sig or CZ offered at the time or offers now.
If it matters to anyone, I am fortunate to own four examples of S&W Performance Center Limited 5-inch target 9mm pistols with fantastic single action triggers and adjustable target sights and I'm not sure if any one of the four shows itself as "more accurate" than the other three, but I will tell you this...
I am also fortunate to own four examples of S&W Performance Center Limited 5-inch .45cal single action pistols and I would pick A N Y one of the four .45's randomly to go head to head with any of the four 9mm's randomly in a show down, and that's the basket I would put all my eggs in.
So search our forums about "PPC-9 versus 952" and enjoy whatever results you find but please don't try to pass that off as fact because that idea is ludicrous.