A lot of people who tell you to buy in one caliber vs. the other are telling you to buy that one because it's the one they own. It's more of them patting themselves on the back, or affirming their own decision, rather than an unbiased opinion.
The truth is both the .223 and 7.62x39 are great. CSA makes good rifles. not only that but they stand behind them with a solid warranty. Not every 7.62 model runs flawlessly and neither does the .223 remington model in every case, but for the most part, whichever caliber you choose, you'll be getting a very good rifle. If the one you end up with has issues, the warranty will take care of it.
Don't let someone try and convince you that simply because the Vz 58 was originally chambered for 7.62x39 that all VZ 58 rifles currently produced in that caliber are perfect. It's not as though all 7.62 models are sprinkled with magic pixie dust which renders the firearm immune from FTF's or FTE's. I've heard from some guys with the 7.62 models about numerous issues. It has nothing to do with the caliber. It's just an anomaly. The same goes for the .223 issues these days because from what I heard, the .223 model issues have been identified and taken care of.
Your choice should be based on which caliber you want to shoot. For me, the .223 remington would be my choice. The ammo is relatively cheap and (this is key) it's abundant. The ammo buying situation for .223 is far, far better than for shooters of 7.62 x 39. And please don't anyone challenge me on it because I'll just point out the proof of whats available currently and how much it costs for both calibres, and then I'll say: "See?"" and you'll go "Oh......ok nevermind". that is Unless you want to shoot corrosive. I also like the .223 round because it has less recoil. I don't mind the recoil of the 7.62 but it makes follow up shots less accurate, and I don't know anyone who would prefer more recoil over less recoil. That would be kinda weird. Heck, if I could have the recoil of a .22 LR every time I shot a 12 gauge slug, I think that would be cool. Although who doesn't love a good shoulder slam once in a while. I know I do, haha.