been shooting both for years. i have 1 russian sks and 2 aks.
both are the 2 most reliable rifles ever built, arguably. well, no its really not arguable. anyone that knows anything about semi automatic blowback, gas operated firing systems will attest to this. the SKS will be slightly more accurate due to its longer barrel. the operating system of the 2 firearms is precisely the same. therefore, functionality will be pristine with both rifles. the ak, as HD said, is nicer in terms of having detachable mags by design. this means that while the sks can be converted to take detachable mags, it will cost you in the reliability dept. (the inclusion of detachable mags on the sks has shown and proven to deter the fierarms feed-ability in some cases). i have a romanian wasr-10. (1 of the cheapest made aks on the market, mind you) people who shoot egyptian maadis ( i have one maadi as well) and russians and chinese mak90's will often [censored] the wasr10's, primarily due to their sloppy fit and finish and stamped receivers. (this can inhibit you when firing rapidly as the stamped receiver heats up F A S T!!!!!!) and can consequently bend under extreme heat. the milled receiver on the russians, some of the chinese, and some of the maadis (mine has a milled receiver) will allow for rapid fire and you dont have to worry about the receiver becoming deformed.
in the end, either rifle is one of the best rifles in the world in terms of reliability. my wasr10 has been every bit as reliable as my Egyptian Maadi and i paid almost 3 times LESS THAN the maadi for it. get either. the ak47 will obviously be worth more, should you ever decide to sell it. but the sks is, IMO, just a fine fine fine rifle. original with a 10 round mag... the thing will virtually never jam. there is a hella nice one down the road. a russian SKS that i am thinking about picking up for $400. you cant beat either one. i have been a staunch shooter of these 2 firearms for years and owned them for an ample amount of time. i hope this post has helped you. i dont know as much about SY knives as HD or some others but i do know Aks and sks's.
