If you are either past the age of 12 or have an IQ higher than your shoesize, it reallys houldn't matter where your gun was made or designed.
That said, the SKS and the M1 Carbine are very different weapons and were designed to do very different things.
The Carbine was designed to replace either a 1911 (or other side arm) or an M1 Garand depending on the situation (it was good for giving to rear line personnel who did not need the very large and full powered Garand, and also it was designed to replace a pistol in order to be a small-ish, light-weight firearm that could be used for both close fighting as well as short to medium range shooting).
The SKS was a primary issue rifle that was issued by the thousands to troops all over the world. While I do not know the history and design of the SKS like I do the Kalashnikov, I do believe that I have read that the SKS was built in Russia to be a short term "bridge" between the older WWII era rifles and the more modern Kalashnikov rifles.
I might be totally off here and I welcome any Simonov afficianado to correct me about the history of the rifle.
That said, both rifles are great; I think they are both about the same in terms of accuracy, with the Carbine perhaps giving very slightly better groups, but with the SKS being much more durable and chambering a MUCH more robust and powerful cartridge.
While I do own a WWII era Carbine, and I do really like the rifle, the .30 Carbine cartridge has some pretty serious ballistic deficiancies, but what it lacks in power, it makes up with ease of shooting and lack of recoil.
7.62x39 is a significantly more powerful round with far more uses, but the rounds are hardly comparable because the 7.62x39 was designed to be an intermediate, full power, rifle cartridge, while .30 Carbine was designed to be very light and fast (in fact, I think .30 Carbine is comparable to .357 Magnum).
Which to buy? I don't know, but this is one of those rare situations where it is quite easy to just get both! You can get a GREAT, brand new Yugo SKS for under $150, and then you can save up for a little while and drop around $600 for a good carbine.