A question close to my heart...
I presently own an Arsenal SAM-5 in .223 with a milled receiver, Arsenal SAM-7 in 7.62x39mm, a Polish PMKMS in 7.62x39mm with underfolding stock, a Bulgarian AKS-74 in 5.45x39mm, a Romanian AKM in 7.62x39mm, a Yugo fixed stock M70 in 7.62x39mm, and a bunch of kits including an M92 krink underfolder (sweet), Yugoslavian M95A in .223 underfolder, SA-85 Hungarian in 7.62x39mm, Polish Tantal in 5.45x39mm, 4 Yugo fixed stock kits, 1 yugo underfolder, and another Bulgarian AKS-74.. also a Bulgy fixed stock kit. I've owned many other AK rifles that I've built or purchased myself.
You could say I have an interest in the AK system. It is how I got into the gun building scene... There are so many varieties out there.
In a built gun from the factory, I have no doubts that the Bulgarian Arsenal guns are the best out there currently available. There are more options in this gun in the AK, then from any other factory gun presently available. You can get milled or stamped receivers, folding stocks (side and underfolder), scope rails, adjustable rear sights, even an ambidextrous safety on the left side, just above the pistol grip in case you hate the regular safety.
For a home built gun, or one built by a gunsmith... I'd have to go with with the Yugoslavian AK's. My M95A in .223 is just awesome. Get this.. it was made in 1997. O.O Wow. My M92 Krink was made in 2005! That means it was manufactured at one end of the factory and cut apart at the other! All the yugo's are equipped with glowing night sights. The 7.62x39mm Yugos are not chrome lined however, and some of them have been exposed to corrosive ammunition without proper cleaning procedures. This means the bores may be less then ideal. The .223 ones though are all chrome lined.
If you were just looking for a fun gun, I'd go with an SAR-1 and avoid the WASR series. Or just build up one of the ubiquitous Romanian AKM's available in kit form for 99 bucks.