A detailed explanation for those who just have to know:
I want a semi-auto rifle of some description for throwing lead at targets and general playing around. But I also want to know that if I needed to use it defensively (I have handguns and shotguns for home invasions, so think bigger), it would have the terminal ballistics to be decisive. Though I would not likely need to use it for this purpose past 150 yards, I can see no scenario where I would choose to use it past 300 yards.
As the primary roll is fun, ammo needs to be affordable. I have plenty of other guns where it is no so affordable. This one needs to be. And because I'll be buying bulk ammo, I will mostly have FMJ available in the unlikely event that I needed to press the rifle into a defensive roll.
Now, a PCC is fine. If it's reliable and trouble feel, and chambered in a powerful enough cartridge that I reload. That would be either 10mm, or .357Sig. Though this is proving tricky to find in a non-AR platform. Some say one design is good and reliable, other say maybe not so much, etc, etc.
Why not an AR? I've had one. It was fine. They don't excite me in the slightest. I hate the charging handle aspect of the design. If I don't like the gun, I won't shoot it. Someone did provide details of a Brownells AR18 upper. It alone is around $800, if I can find one. Then I need to address the lower and all that business. No problem for someone who enjoys assembling ARs, but an expensive headache to me. No AR.
I already have a Mini 14, I have a reasonable pile of 5.56. It's okay, but again I'm not that excited. I keep it because it's nice to have it around. It gets shot occasionally. I've previously had an M1 Grand, and an LRB Arms M14SA. Both fun, but big, heavy, ammo is a bit too expensive for my intended use.
I don't really want to spend more than $1000. I don't mind iron sights in the slightest (I used them on a the rifles above). I've never had an AK, and I think the design is really interesting. I know there are some out there that use a stanag magwell adaptor and come chambered in 5.56. PSA sell several and recommend using pmags. But obviously the design was originally intended for 7.62x39. The tapered cartridge seems a benefit to extraction, and parts are easier to find. 7.62 is the direction I had intended to go if I buy an AK (which I may or may not).
So this thread and this poll was about ONE factor in a list, to help me determine if there was any real benefit in straying from 7.62x39. It seems it is not a significant one.
Some may argue that ammunition cost or availability makes one a better choice than the other. Perhaps they're right, but from what I see, the market doesn't seem stable enough to predict that.