The best weapon to choose depends on a number of factors.

First, your weapons should be DEFENSIVE weapons, not offensive ones, at least during the initial weeks or months of a major event.  Ideally, you’ll NEVER fire them, because you’ll be expending every effort to avoid confrontations.  Remember, there isn’t likely to be EMT/ambulance services to take you to a nearby trauma center if you get shot!  Anyway, keep in mind that you aren’t equipping yourself to be an assault team, charging IN to danger.

Second, your terrain can make a difference, because the primary difference between a 7.62-based weapon and a 5.56-based weapon is effective range.  Those in the Plains states may be better off with a 7.62-based rifle, but if you’re in a heavily urban/suburban area, or one that’s heavily forested, 5.56 will be sufficient.  Certainly, you can argue the superior penetration from 7.62 in many mediums, but that’s more of an issue for offensive missions than for defensive ones.

Third, the number of people in your group can be a factor.  In the military, even down at the squad level, you have several different types of weapons that are designed to work together.  If I had 3 or more people, I’d prefer one of them to have a 7.62 weapon and the others to have 5.56.  If necessary, the 5.56 shooters could create a volume of fire, while the 7.62 shooter takes aimed shots or shots at enemies behind cover.  For a lone actor, I would default to 5.56 unless you have specific reasons which require 7.62, which might be terrain or other considerations in your local area.

Ultimately, it will be your other skills that will account for 95+% of your odds of survival.  Having the necessary supplies to get where you are going, having TESTED and familiarized yourself with your gear, having your group prepared on “on the same page, and evading everyone else’s notice completely is FAR more important than the type of gun you choose to carry

-Troy

Many, many enemy have taken hits at longer range from M16-based rifles and were not incapacitated immediately.  It makes little difference if they suffer mortal wounds that cause them to die an hour or a day later, if they still have the ability to radio in your location for others to attack.  Even if that attack *didn't* mean artillery, MLRS, or air-strikes, it could still mean being surrounded and killed.  That's why load selection (as well as barrel length) is SO critical with 5.56 weapons.

Again, as a lone actor, you're *probably* best off with an AR over a 7.62 rifle, unless you have very specific requirements that dictate otherwise.  And you should do everything possible to AVOID confrontations, making your choice of weapon irrelevant.

-Troy