"Better" is a very subjective term.
Better at what? Hunting? SHTF? Plinking? Long range shooting? 30 rd mag dumps?
You have to look at how you want to use either rifle. It may even be a matter of how each rifle feels when shooting (ergonomics if you will).
One thing the AK and SKS have in common is, all things being equal; both are very reliable and will run a long time in adverse conditions. You can't go wrong with either one at that department.
I have not owned an AK in a long time but currently own a Yugo SKS. Here is my take on each one.
Yugo SKS:
They are well built and have reasonable accuracy for what they are. I added a Tech-Sight, which made the rifle even more shootable, so to speak. Reloading with stripper clips can be fast with just a little practice. Personally, if I was in a high stressful situation, I believe I could reload a SKS easier and faster then trying to insert a new mag in an AK (granted I would have to reload sooner with a SKS). The Yugo is a long and heavy rifle but that is not a big concern since it is mostly a range rifle/plinker. It's for fun. Having said that I would not feel unarmed if the SHTF and that is all I had.
AK (pre-ban Polytech Legend. Sold long ago):
Lighter and more compact than a SKS. Milled receiver made the rifle very durable. Mags are well built and reliable (never came across a bad AK mag). Easy to shoot and even had a decent trigger (no trigger slap either). I never shot the thing out to 100 yds but it would eat the center of a target at 50 - 75 rds. In a SHTF situation, this would be the one to grab. Having said that I never really did much range time with it. Fun to blast stuff with but once I knew it worked I did not bother with it much.
So, which is better for me? Since having the Yugo, I never had much of a reason to pursue getting an AK again. The Yugo is a great at tossing soda and coffee cans around in the desert. That is what I got it for and it does a great job.
For more serious range work, my money has gone into ARs. In a SHTF scenario, the Bushmaster gets grabbed first. This is not a AR vs. SK statement. It's just that I have always been more comfortable with the AR platform. From plinking to bench shooting I have been very satisfied with my ARs.
To sum all this up:
SKS + ARs = No real desire to have a AK
SKS w/ no ARs = I would have both a SKS and an AK to cover all the bases.
So no matter what, I would still have a SKS. Which makes a SKS better for me.
Which of course, does not help you whatsoever. Get both, it’s the only way to be sure.