Really? I was under the impression that 5.45 was the standard issue for many countries, in fact replacing the 7.62mm. Not the same variety of mags but a quantity out there still at near the same price. And its less than the 5.56 by eleven hundreds of a milimeter, but the Reds choose to replace the 7.62 with it? I'm not particularly attached to either as a potential new rifle, but I don't want to blindly slander available options.
You certainly shouldn't take my word for it, but heres the rationale. The combloc went to 5.45 for the same reason we went to 5.56 (and any thoughts of us standardizing to make life easier for the grunts?

). Anyway, flatter trajectory, less recoil, less weight. Great. Still, less terminal energy. Now, we are thinking about going heavier, .308 again, while they are going lighter. Take your pick.
Still, for a cheap, easy to feed, fix, replace, do anything, shtf/hunting rifle, I'd take the old AKs in a heart beat. More availability of everything as I posted, plus enough gun to hunt with. If you want the smaller and lighter caliber, with more accuracy? I'd go AR.
Any of the three you'll have fun, but If I could choose free of charge, between an AK-47, an AR or an AK-74, a .545 would be my last choice. Honestly, I'd flip a coin between the AK and AR price be damned. Just my .02.
FQ13