I own both guns, bought both used. G17 came from a consignment deal at a gunstore, have no idea of the history behind it, whether it was abused, etc. CZ was a range rental, has cosmetic blemishes, etc. Anyways, upon shooting both, they are what I would equally accurate, meaning, both are much more accurate than I am. They are both more than "combat accurate". As for other qualities, I don't know if this is because my CZ in particular was a former rental, but it jammed like crazy at first. In fact, I remember renting this exact gun before it was for sale and it wouldn't go more than a couple of rounds without jamming. They were mostly FTE's if I remember correctly. After a thorough cleaning (by my standards anyways), it functions much more reliably. However, it is still not what I'd consider to be 100% (which my G17 has been, with the exception of the slide not locking back after a magazine is emptied a few times). For this reason, I am personally hesitant to use as a defensive weapon, and it has been relegated to range-gun status. Another reason for its less-than-stellar reliablity may be because I am limpwristing it. This may be because my particular CZ has hogue wrap-around grips which make it a little bulky feeling, and hader for someone with smaller hands like me to get a really firm grip on. Another thing I dislike about the CZ is the sights. The little dab of white paint on the front sight is worn off, and it has rendered the sights all but useless. Now, this may be true of all sights with paint on them, but I don't foresee the plastic Glock sights ever having this problem. Another thing is that the CZ seems pretty big for a 9mm, a similar compaint to the one people frequently use against the Beretta 92FS. Now, the G17 isn't a compact pistol by any means, but it is much less bulky than the CZ, to me anyways. However, the CZ is not without its merits. It is, like I mentioned earlier, VERY accurate. It also has a very smoooth DA trigger, and SA is great as well. It also allows for cocked and locked carry, as well as DAO carry. If I can get the sights fixed, or repainted as the case may be, and the extraction issue worked out, I may shoot it more frequently and like it much more. Until that happens though, the G17 is my go-to gun for 9mm shooting.
The G17 on the other hand, has a less than stellar trigger, and I don't know if it's just my imagination, but it seems like on the last round of a magazine, the trigger gets super heavy. Also, not exactly what I'd call ergonomic, but, with practice, and since you already own a Glock, it will point and handle more naturally. Like I mentioned earlier, it is also very accurate. Lightweight, somewhat more compact than the CZ, and more reliable. To me, they are equally easy to disassemble and clean. Like others have said, they are both good guns and you really can't go wrong with either, but the Glock seems to be more worry-free for me.