"So the question is with the same optics and ammo would the sks or ak do better ?"
I don't know for a fact, as I don't own an AK at the moment, just a couple of SKS's, but, if I were to guess, I'd definitely say the SKS would be more accurate. It's got a longer barrel than the AK, a little more weight behind it....plus, with the SKS you're looking at, you can shut off the gas valve to the grenade launcher, making it in essence a manually operated single shot. Some folks say this gives it more accuracy, but I personally can't tell too much.
The mount on that SKS is screwed directly to the receiver, it's not a cover mount type, so it will hold it's zero very well. Keep in mind that you will NOT be able to use stripper clips, as that scope is too long and sits too far out over the bolt. This may not be an issue to you, but you'll be loading the 10 rd mag one round at a time. You'll also probably want to get a shell deflector, to keep rounds from hitting the scope. I think Tapco may have them, or SKSman. With this setup, I'm also wondering how easy it will be to take the receiver cover off to clean it. Also, an 8 power fixed scope on an SKS just seems overkill to me, big time. I think 4 is better, 6 is way stretching it, and 8 is too much. There are those that think any kind of glass on an SKS is unneeded. I'm not one of those.
I like SKS's, and I like sniper type rifles, but I don't think they go well together in one gun. With an 8rd scope and not being able to use stripper clips, it kinda takes away from the SKS's purpose. And the 7.62x39 is not a long range round. That said, it would be a neat gun to have, but I could find better ways to spend $350.