Well the fact of the matter is bullets do damage when they meet flesh. It's not too much of an issue whether it's 5.56 or 7.62. When you start moving up in the calibers then we are talking. .308 will knock you down with a purpose, but with the debate being between the standard calibers of (what I am assuming we are talking about is the AR and AK) platforms they both have strengths and weaknesses. 7.62 has a good amount of kick at medium ranges, but overpenetrate for some desired scenarios. If it's not an issue then go ahead and use 7.62 to turn the badguys' cover into concealment. Neither one of them is gauranteed one shot one kill though. I've shot bad guys with one round and turned the lights out and I've put 10 rounds through a guy that was still standing (thank god my buddies in the stack also shot him about 10 times each upon entering the haji house). Either platform will get the job done. The issue should be follow up shots. Make their medic work for it. We all know 5.56 is like shooting a BB gun making follow up shots into second nature, but 7.62 isn't an a** kicker either when you add a little M-A-N into the equation. They both do the trick which is why both of them are in use today. I prefer 5.56 because it was the round I used to arrange meetings between bad guys and their 72 virgins, but I have no doubt in my mind that if I had used 7.62 those meetings would have still taken place. It's a good topic though. Not sure all the ballistic info justifies the effectiveness of the round though. .22 LR can kill just as good. Ballistics gel is good for an image or understanding , but "magic bullets" change everything. Just know your system and use it in such a manner that allows you to continue to breath after stopping your enemy from doing the latter.
The basic concept differs wherever you are. Always remember "Know your target and what is behind it" - John Everymarine. Let the good lord above decide which round worked better and just move on to your next target.
"A man who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself."- John Stuart Mill