I have at least 8 SKS' from Russians, Yugo and Chinese and if I had to buy another one, I would look for the following:
1. Is the gun complete - bayonet, cleaning rod, etc, etc?
2. Are the main parts machined or stamped and is the barrel pinned or threaded (easy to determine).
3. Is the bore in good condition - lots of corrosive ammo for this gun available?
4. Do all the numbers match (will get you a better price if you ever sell)?
5. Does the action cycle smoothly?
You can find a lot of these that have been sporterized with synthetic stocks, scopes, etc, and these are fine for hunting, plinking, etc, but might more difficult to get your money back, if you ever sell.
My choice would be to buy a Russian model (if you can find one) followed by a Yugo and then a Chinese. Russian models will keep their values better but from my experience, a Yugo is the better quality SKS. You will also find that the early Chinese models are relatively of fairly decent quality with machined parts, etc. And finally, you will find two types of bayonets - the blade one and the spike one - I prefer a blade type.
I realize that some of these factors might be of no interest to you so in the end, you will have to decide what is best for you keeping in mind that the price range might go from just over $100 for a Chinese model to over $500 for Russian model.
Good luck!
Duke1