Neither. My opinion.
The CZ is a faily priced pistol with average to good accuracy. Making it into a super accurate shooter would exceed the price of the basic gun. It has a decent 1911 type lockup with a front barrel bushing, but most top shooters don't choose it.
The Sig is a highly overpriced and over-rated pistol with decent accuracy. It has the same type lockup as Glocks, M&P's, XD's etc: No front barrel bushing. It is a decent shooter but the slide is tall in the hand. Forget about after market parts, barrels, etc, somewhat like the CZ.
If you are not enamoured of the 9mm cartridge, forget the CZ and the Sig and buy a quality 1911 in 45acp. With a tight barre, slide, and bushing lockup, the accuracy is unbeatable. Colt's Gold Cup National Match pistol was the top of the heap for a reason.
Should you want a decent affordable pistol that has pretty good accuracy chambered in 9mm, you cannot beat the Glock17 or the S&W M&P.