Well, the American ideology behind guns is that, if you arm the civilian populace, then the government will have a much harder time developing a tyrannical rule, or walking over the Bill of Rights. I do honestly think that the 2nd amendment is in place to prevent America from becoming another china, or God-forbid, Australia!
But back on topic, I'm going to have to say technically neither. Instead, I offer the AK-74 as my answer. Why? Well, you have the same dead-reliable Kalashnikov-action, but with a cartridge (5.45x39mm) that has a greater effective range than the AK-47 round (7.62x39mm) and greater inherent accuracy (higher muzzle velocity, longer bullet), yet still has more cover penetration and reliable yaw/fragmentation characteristics than the NATO/American round (5.56x45mm). To boot, the proliferation of the AK-74 has generated so many neat variants, like the Polish Tantal and Bulgaria's 74s. Even more beautiful is that, with most Ex-Warsaw countries joining NATO and switching to 5.56x45 rifles, they've massively exported their surplus and leftover guns, and now the average American can own them as well. http://www.jgsales.com/index.php/rifles/ak-47-and-rpk-rifles/cPath/209_214
It doesn't hurt that J&G is selling surplus 5.45x39 in 1080rnd sealed-tins for $150 a pop!
My written fellatio of the AK-74 aside, I do adore Eugene Stoner's design as well. It's light, simple, and as long as it's taken care of halfway decently, it's just as reliable as the AK. the cartridge is a little lacking though right now as the round was designed for a 20" barrel and now with the M4 carbine that's been chopped to 14.5". Due to the Hague Convention, the US cannot use fragmenting bullets as they've been deemed excessively cruel. So the 5.56 round work on yawing. when the bullet hits flesh, it begins to yaw and rotate, creating a massive wound cavity. Problem is, it has to be going at least 2700fps to do this. Out of a M-16's 20" barrel, the threshold where the bullet's fps drops below 2700 is around 150yds. Out of the M4's 14.5" barrel, it drops to less than 90yds. Body armor further complicates matters, as it will slow the bullet to the point where it might just go through the body cavity and not do much damage. (see Viet-Congs wrapping themselves in duct-tape vests and the 5.56 rounds just flitting through, while the crazed jungle-commies continued to charge)
The 7.62x39 cartridge uses sheer mass (double the bullet weight of 5.56 NATO) to do damage, and it works, at the expense of heavy recoil and inherently shitty ballistics. the 5.45x39 though, basically takes the flat ballistics and low recoil of the 5.56 NATO round and enhances lethality by using a steel core and a jacketed hollow-point. When the cartridge hits a body, the steel core shifts, pushing forward into the hollow cavity and causing the bullet to yaw much sooner than the 5.56 round.
So, in essence, I would rather have a (well-built) AK over an AR, but both are sweet rifles.
I feel I should point-out that, the AK has a fairly undeserved reputation for poor accuracy. Yes, tolerances are high and the barrel is relatively thin-profile, but regularly AKs get 3-4" groups. As well, the factory iron sights are atrocious, and installing either a Tech-Sights rear sight or a Krebs Custom scope rail greatly enhances the sight picture. antoehr thing is general build quality. Almost always, a genuine Russian-made AK (such as a Saiga hunting carbine) or an Arsenal brand build, will be miles better than, say a parts-kit Romanian WASR or whatever shit Pakistani gunsmith specials our troops face in the middle East. In general, for average engagement range, which is rarely more than 200yds, the AK will hit COM on a human target.