[quote=RPCWhite]
Well see though it is a trade off. Sure the AK is powerful, But you get more accuracy with like the M4. It may only take you 1 round with an AK to kill a guy, but if you are a trained operative or something then you can get those three rounds on center mass pretty quick. Doesn't matter how fanatical you are, you get three rounds in your chest and one to the head you are dead. I like Accuracy, power i could really give a shit. and most likely we will be engaging things in long or medium range in the beginning. Close range combat with a new type of species? That would be fairly deadly. This is of course my opinion. But you would want to learn their physiology first before you were going in close enough for an AK to definitely not miss it's target. And by the time we get to mutons we will probably have some sort of alien weaponry.
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Yes it isn't a good idea to get into Close range combat with a new type of species... but the Berserker can take a plasma sniper rifle shot (Hell, plasma pistols can blow away entire walls) and continue to charge you. Like it or not, he's going get close to you. Even the sectoids end up being pretty close to you in xcom, remember, all they need (on the harder difficulties at least) is a single shot to knock your recruits dead and given their bad accuracy the sectoids probably don't want to end up in long range engagements (They're using pistols, we're using rifles, they are going want to close that distance)
Also, in EU you research alien weaponry super fast. Unless we're going to make massive bounds within the first of these 'seasons', we're probably going to be using ballistics for a while
Shooting someone in the head is a lot harder than hitting them in the torso, soldiers are taught to aim for the center mass as a result. Jihadists have been known to continue fighting with bullets in them, humans are more resilient than we give ourselves credit for
The size of the bullet seems to matter to the SAS and the US marines, both have argued a case for larger bullets to be used:
"The bullets upgrade – and a new range of rifles designed to fire them – were recommended in a top-secret report on SAS operations in Afghanistan. It called for a return to a ‘shoot-to-kill’ policy and for heavier rounds to be issued to troops. The report’s authors described bloody clashes with Taliban jihadists who managed to ignore their bullet wounds and carry on shooting" - Daily Mail article talking a bout a recommendation by the SAS to upgrade up from 5.56
"‘But this backfired against the Taliban. The 5.56 mm rounds did not take a big enough chunk out of them, allowing fanatical insurgents to keep on fighting despite their wounds." - SAS regiment insider
"They [US Marines] all hate the 5.56mm (.223) round. Poor penetration on the cinderblock structure common over there and even torso hits cannot be reliably counted on to put the enemy down." - Paraphrased to a reporter by a father after talking to his marine son (In defence of the 5.56 however, he mentions that autopsy reports show that many insurgents are drugged up)

Also, while saying three shots to the chest will put an enemy down... on classic mode a sectoid who is wearing nothing has nearly as much health as an armoured rookie, so I gotta argue that here 7.62 vs 5.56 is much more important to consider than on a conventional battlefield, because we will end up fighting aliens who will just blink and say 'What...' if you shoot them with ballistics. Thin men on classic have just one less hp than a soldier in body armour.

Basically, my argument is

7.62 vs 5.56 is much more important because it seems even the basic aliens are pretty tough considering they aren't wearing armour. Do we want to be hitting them more or packing more punch when we hit them?
These aliens obviously have superior weapons. The sectoids are terribly inaccurate however, so we likely will end up in CQC with them because they are likely to try and push up to counter this
As a result, the trade off is more important than irl. 

Basically, we're talking a choice between EW's reaper rounds vs standard rounds (though slightly less ridiculously inaccurate than reaper rounds were lol). Both have their ups and downs, and here it's going to be painfully obvious. If we miss that muton, he'll probably melt us, if we fail to kill that berserker, he'll crush us.

As for side arms, we'll likely bring the side arms of our country and their respective service branch. So if you're character comes from a poorer country you'll likely be using older weaponry, while if you come from a richer country you'll be using modern weaponry. You're mileage may vary as a result