Here's how some people can get confused:
1.) There are plenty of US aftermarket parts for the SKS. These include detachable magazines with the same curve as the AKs, but with a "duckbill" on the front. There's another kind without the duckbill that requires an insertable adapter.
2.) There are less common models of the SKS that have been modified to feed from AK magazines. These are known as the Model 84 (pre-ban, with bayonet) and the SKS-D (with 16" barrel and standard or thumbhole stock.)
3.) There are aftermarket stocks for each made by the same companies which make the two harder to distinguish.
As far as which is better... It's a tradeoff.
I personally prefer the feel of the SKS's action when firing. The AK is a little harder to control. Harder to site up, harder to stay on target (then again, I don't own one, so I haven't had tons of experience.)
Basic tradeoffs are that the SKS is designed for a 10 round mag, whether or not you put a larger one in. That means it wasn't meant for the sustained rapid fire that the AK is. SKS is more accurate. The aftermarket hi-cap SKS mags are harder to insert than the AKs, and cost a bit more. Though if I had a standard SKS, I'd use a fixed mag with stripper clips (I have the D model.)
Trust is earned, not... GIVEN away. - Worf