There are small differences between the original and the clone, but it happens all the diffs are (for me) in favour of the NP22. The trigger reset is much shorter (in my gun) than the Sig, and the trigger itself has serrations - the Sig trigger is smooth, and my finger can't get a good grip on it. I got the Sig after the NP22 for US matches, but found out I didn't like the Sig after all, so someone else is using it..
re accuracy - well, yeah, I mean, the Sig IS more accurate but we're talking IPSC in Ont/Canada where shots over 20m are almost never required, and shots over 15m are rare. if I started to see plates at 30+m more often, I'd probably need to change guns (and change my shooting style, haha), but in the past year, I've never seen a situation where the gun wasn't accurate enough for a shot. The only time I actually had problems was trying knocking down minipoppers at last year's Triangle, but it was a combo of the dark background and the really wide sights I have, not the accuracy of the gun itself.
The NP is Aluminium in part, I think, it is lighter than the Sig...
Now the Std disclaimer - with Norincos it's hit and miss I hear. I got mine from DARK, paid a little extra for him to take the guns apart to make sure all the little bits and pieces fit, and I haven't had any problems. So take my comments to apply to only those NP22s obtained from Rodger with the similar treatement - not any Norinco out there...