I have both, and think that it's a bit of an apples to oranges comparison.
If you want a rifle that you could buy and shoot as is out of the box (well, maybe after removing cosmoline if heavy), the SKS is cheap, reliable, and accurate enough to test one's skills in various field positions. You could practice at the range out to 200 (maybe 300)m, though practical hunting ranges for deer sized game would be less (100m for sure, maybe 150m). The ammo would be cheap, and the rifle easy to maintain.
The M14S would probably require more work. For starters, most have the barrel timing/indexing just a bit off, meaning that unless that's fixed, you may have to adjust the sights considerably to hit centre at a fixed range, with variations on POI at further distances. In many cases, the rear sight does not click when adjusted and may not necessarily hold true anyhow, possibly requiring a USGI replacement or use of a scope.
The M14 would be better suited to scope mounting (versus reciever cover mounts on SKS that just don't hold zero too well, or LER mounts for SKS that I cannot comment upon). It would have the accuracy to take advantage of a decent scope. That said, the cheapest mounts (no-name Marstar, B-Square) will cost about $100, plus well over $200 for a 10X Bushnell 3200. Many people here question the effectiveness of the cheaper mounts, though I'm still too inexperienced on the matter to tell the difference.
The M305 would be good for shooting game larger than deer, and good for hunting or target shooting beyond the range of the SKS.
.308 and 7.62 NATO will always be around, if not cheap, whereas the cheap SKS ammo may or may not be a permanent thing. The .308/7.62 NATO probably offers more possibilities for a reloader to custom a good load for their rifle, whereas I wonder if one could get as much improvement in accuracy out of tailoring loads for an SKS (though sometimes this can definitely work, depending on the rifle).
A new shooter just wanting to have fun, or a bush rifle for deer, go SKS. A new shooter who wants to shoot Service Rifle matches, use decent optics, hunt deer or bigger game and possibly at further ranges than 100-200m, and/or is willing to reload or tinker with their rifle to make it shoot better, go for M14S.
And of course, if you really want to deck out a rifle, the M14S wins hands-down. I'm not knocking people who choose to pimp out their SKS with accessories, but it seems a questionable use of money insofar as it contributes little or nothing to accuracy, and in the case of an original Russian, Yugo or early Chinese military carbine, it's a sad loss of the rifle's historicity.
I'm glad I have both.
Frank