OPOSSUM, uh partner the SKS is magazine fed as well...... its kinda a prerequisite for a semi auto unless you have really fast fingers.....
The SKS has a far more complicated FCG, closer tolerances between bolt carrier and receiver rails equaling easier to dust/dirt foul.
The SKS was used primarily as a stop gap weapon to arm "volunteer" forces in order to make up for a shortage of AKM pattern carbines, it served the exact same function for the Russians and the Chinese it was never issued as a first line weapon, the FAL was the rifle of choice actually used by both sides the Brits with their semi only version pitted against the FA version in the Balkan isle action.
The AK was designed with looser tolerances specifically to address reliability problems with the SKS design under harsh conditions, your comparison of a rifle used for your HOBBY target practice at the range can hardly be any indication of battle field reliability...... however we don't have to rely on anyones extremely limited experiences with a USA based privately owned target rifle as all one need do is look around the world..... what rifle was actually issued and used in the largest numbers by the armies of some of the least trained soldiers in the absolute worst environments............ and that would be? oh yea AK-47 or AKM 47
Fill your SKS receiver with fine sand (your really gonna have a hard time getting that fixed 10 round mag cleaned out, and don't forget to get the dust and sand out from under the bolt hold open as it only takes very miniscual amounts there to lockup the mag follower trapped under the frozen bolt hold open in the SKS rendering your rifle inoperable
yea its been tested, with the AK ya simply remove the fouled mag and insert another, with the SKS if a sand granual gets between bolt hold open slider and receiver you must detail strip the rifle and punch out the Trigger group front pin and drive off the BHO to clear it.
Some of that sand got into the SKS FCG? oh what do ya mean your sear is now locked solid?? Oh yea that was another common problem but no worry, now its not like an AK where ya can just pop out 1 axis pin and clear it (if the AK had a sear to become fouled that is, which it doesn't), with the SKS again you will need to strip it, now drive out the retaining pin (duck! the enemy is still shooting at you while your tryin to repair your weapon) now ya will need a vice.............. ohh yea....... no field repair ability with the SKS that would be WHY it was never adapted as a front line infantry rifle by ANY country........ ya really gotta look at the criteria for the OPs question not try to judge based on experience on an American based rifle range.........
the SKS is a great rifle for what it is, a stop gap to arm troops that are not formally trained and who do not require the total reliability of the AK otherwise...... Russia would have selected the SKS over the AK for use spanning how many years?? its a fun range gun and a great second line semi auto weapon.......... but its no match for the AK when it comes to reliability in adverse conditions or ability to be repaired easily in the field...
And a full auto "SKS" was fielded by both russia and China the Chinese found that it took more than adding Detachable AK mags and Full auto capability to match the AK thats why the T-68 never out produced the milled AKs issued by China...... WHY? cause the SKS over complicated FCG and reciever tolerances made it very un-reliable compared to the AK
And as to the original question, yes someone has done a test...... Russia, China, Korea, Yugoslavia, Albania, Iraq........ they all determined that the AK was by far the more reliable and that the SKS was better suited for second line troops than front line use...... based on reliability testing