The CETME/G3 is the most reliable of the .308 battle rifles. The Mexican Army uses them standard issue if that tells you something about them!
The only MAIN downside of the CETME compared to the other two is that the sights only go out to 400 yards, so for 500 or 600 yrd shots you'll have to Kentucky windage it. However, CETME's reliability (a good one, not one of the imported Century pieces of junk) is right up there with the AK, and it is in .308 caliber which easily beats the AK's 7.62x39 in terms of stopping power, accuracy, and range. Not to mention that the AK is seeing ammo supply problems in the US NOW! Imagine trying to obtain ammo during SHTF! Meanwhile .308 is NATO issue, Mexican Military issue (for those of you on the south of the border) and can be found at any gunshop, Walmart, or store that sells ammunition.