What are you going to be using the rifle for?
If you are just looking for an inexpensive beer can blaster it is hard to beat the WASR10. They are easy to identify because they dont have the oval shaped "dimples" on the reciever at the mag well. The biggest advantage to them is the fact that they are the only AK's to reach the retail market as a complete Com Bloc rifle. In it's original form they are only designed and constructed at the Cugir Arms works in Romania to take a 10 round single stack magazine. That is how they can import the complete rifle into the US. Century then opens up the magwell to take standard AK magazines. They will come with the Romainian chrome barrel which you wont get on any of the Century builds since barrel importation has been banned.
Things to watch for on a WASR:
1- Sloppy mag well. Sometimes the beavers at Century get a bit rambunctious with a mill and the magwells can be a bit loose. A bit of side to side play is acceptable but accept no fore and aft play of the magazine. It can lead to feed issues.
2- "Canted" front sight. When you look at a WASR check that the sight base is straight with the barrel trunnion and rear sight. A pretty good clue at first glance is to see how far the sight post is centered in the sight base. If it is pretty well centered that is usually a good sign. And just because the FSB is tilted a SMALL amount that does not mean it is not a good shooter. If you get one that has a cant to it shoot it before you decide to "fix" it. I have seen some that were canted pretty well but they were spot on as far as shooting-usually it is more of an asthetic issue.

For a beater AK/ truck gun they are pretty hard to beat. I had an underfolder WASR and flat out abused the crap out of it and it never once hiccuped.
You can refinsh the wood on them and clean them up pretty well and have a decent looking rifle for not a ton of dough.
As for the rest of the Century AK's keep this in mind: They are rebuilt rifles and the rifle is going to be only as good as the builder. I know Century gets a bad rap sometimes but if you take a minute and look it over pretty well and have a few to look at you can usually pick a good one.
The rebuilds will NOT have a chrome lined barrel usually as they are a US manufactured barrel. Century builds a lot of rifles and sure, a bad one will get through now and then but for the most part they are decent rifles. Besides-even if you get one with issues Centurys customer service aint half bad.

If you are able to find a Vector AK built in Utah they are also great buids out of Hungarian, Bulgarian and sometimes Polish part sets. They are out of business now I believe but if you keep your eyes open you can find one here and there. Too bad-I have a V-93 from them that is every bit as well built as an original HK93.
Vector did well with their AK's.

If you want to step it up a notch the converted Saiga's by Arsenal and the original Arsenals are great rifles. Arsenal in Las Vegas takes the Saiga rifles and converts them to the original AK style. These are true Ishmash, Russia rifles with hammer forged barrels. About as close to a Russkie AK that you can get. The other Arsenal rifles are Bulgarian and are are of great quality.
The Chinese MAK 90 is a great rifle also if you can find a clean one.
The Egyptian MAADI is a very accurate copy of a Russian rifle as they are built on Russian tooling but the quality is all over the place and the painted finish on them is total crap. Dont buy a MAADI unless you can inspect and shoot it.

For the top of the line you cant go wrong with a pre ban Bulgarian or Hungarian (or just about any pre ban rifle) They are authentic AK rifles that are built on original AK tooling in Comm Bloc arms factories. But you will pay a premium for one, typically a grand or more. They are more of a collectible than a shooter.
Some of the ban era rifles can be had for around $6-800 and are great if you know what to look for. Typically they will either have no muzzle device or threads or a permanently pinned/welded brake on them. Unless somebody has converted them they will have a thumbhole stock on them. If they dont they have been converted and you need to keep 922r in mind-Make sure it has the correct US parts count.
The Hungarian SA-85 is stamped and a great rifle.
The SLR-95 is a milled Bulgarian and are awesome shooters.

As far as the plethora of off the wall builds that you see again they are only as good as the builder. Stay away from what is known as a "Screw Build" - they used screws instead of rivets and I have yet to see one stay tight in the long run.
Quality is all over the place and frequently I will see one with rivets that are not compressed (set) properly.
Anybody can put together an AK in their garage but you need to know what you are doing for a QUALITY rifle.(Not trying to flame the homebuilders out there-Most of you guys do very well)
A lot of people use modified bolt cutters to set the rivets and while it looks right they dont have the power to set the rivet correctly.
In the Comm Bloc factories the rivets are set with hydraulic or pnuematic rivet sets that set them all at once and the rivets are set hot.
You just cant get that out of bolt cutters. They just dont have the force to dimple the recievers into the trunnions when the rivet is set. This keeps the reciever/trunnion tight as the reciever flexes during firing and the rivet does not have to carry the full stress of firing. If it does it WILL loosen over time and allow movement between the reciever and trunnions.
Go with a factory built rifle for your first AK.