I have owned both and shot both, and prefer the CZs... but primarily because they fit my hand better and seem to point better for me.
The disadvantage of the CZ, for some folks, is that there is a longer trigger pull.
I find the DA/SA transition to be much smoother with the CZ. My scores in IDPA seemed to jump upwards (lower times) when I switched to a CZ-75b, and I've since changed to a CZ-85 Combat.
(The Combat is in the same price range as the SIG, so there's no price advantage.)
The only SIG I've got now is P-210, which is superb, but its on sale (on consignment) at my local gunshop. The European style mag release is a pain, and I want to shoot other guns in IDPA.