I've tested several variants and derivates of the AK
I'll tell you which are the best of them:
From Izmash, Russia
1)AKM-it's a classic and can be easely updated.Turn it to tactical by using a kit and you'll obtain a badass rifle.
2)AK 101/102-made for export.Chambered in 5,56x45....the most common caliber in the US.Up-to-date, but it can be still improved
From Zastava Arms(Former Yugoslavia, now Serbia)
1)M70 series:It's the best AK derivate ever made.Chambered in 7,62x39, it has a better gas system, longer barrel, the same reliability, can be easely updated and modernized.Accessories can be addeded(to make it almost recoilless).
I have tested and modified almost every type of AK made by russians, serbo-croatian, hungarians,etc.
My weapon of choice?
The Zastava M70.Absolutely the best!I prefer it to the original AKM.
Things to avoid:
-Buy the Chinese type 56 (from Norico,bad quality...it jams a lot).
-Buy a Hungarian AK (poorly made)
-Buy an AK in average status(Even if you can abuse and AK rifle in several ways, it doesn't mean it will work perfectly if you do it)
-Buy an AK without checking the integrity of the barrel, gas piston and its rotating bolt.Even the mag insertion should be checked(If it fits as it should)