Most Ak's on the market are Romanian WASR AKs. The SAR-1 is the standard Russian 7.62x39, the SAR-2 is east European 5.54x39, and the SAR-3 is NATO 5.56.
The Romanian AKs are a pretty good buy but the furniture is cheap and the machining isn't a work of art. I had a SAR-3 and traded it for a SAR-1 because I wanted standard AK parts, and reliability. I'd say these represent the typical AK found worldwide.
Chinese NORINCO AKs are pretty much in the same category.
Better AKs are produced in Bulgaria, Hungary, and Russia, but you'll pay more. Plus there are American made AKs available now too, but again you'll pay more.
Basically, the AK is a hard working, reliable weapon regardless of who makes it. If you stay with the 7.62x39 you'll find plenty of parts to customize, upgrade, or repair your rifle.
A good web site to get info on the different makes and models of AKs is at:
www.ak-47.usWhatever you get...enjoy it.