These are two different animals. One is a polymer framed, striker fired pistol and the other is steel, DA/SA with a hammer.
I think both are excellent, but it depends on what you like and prefer.
I don’t have a CZ anymore. (had a CZ 75B full size) But I do have the FN 509 midsize, and I absolutely love it! Don’t let all the haters sway you. The 509 midsize has a ton of great features out of the box and my sample of 1 has performed perfectly with all kinds of ammo from cheap steel cased, aluminum cased, brass cased, 115, 124 and 147gr both ball and hollowpoints.
It has become my favorite polymer striker pistol. It just fits my hand perfectly and I can reach the mag release and slide stop with ease. Hand size varies and everyone has their preferences, but if you can rent one at your local range, I highly recommend you try it.