I skipped both of those in the CZ and went with a 6.5 Grendel, after having built a few in AR platform. I also have AR's in 5.56 and a .223 Remington 700 varmint special, not exactly a walking around gun, but fun.
Back when 6.5 Grendel brass was hard to find and very expensive, I picked up a large supply of IMI 7.62x39 brass and resized to Grendel for fireforming. I have not tried any in my CZ yet, but the loads to fireform function through my AR's just fine, cycling the action, chambering the next round, ect. Nowhere near the velocity, or the accuracy of a properly formed case, shooting very low in comparison, but still fun to plink with, using a lot of "Kentucky windeage".
My idea of ideal would be one of the little 527 FS carbines in 6.5 Grendel