The AK model has been proven through extensive use and testing as a remarkably durable firearm. It holds up even when it should be jammed up by sand and mud and God knows what else. That is why it is such a reliable weapon for use in the Middle East. That being said, the wood features are a nice touch, but not necessarily the most functional, and the iron sights can be slightly difficult to use.
Meanwhile, the AR model sacrifices a slight bit of durability, but is manufactured in such a way that allows for customization. It is lighter, and more versatile. Well made custom AR models can potentially be as durable as the AK, but the rails allow for lots of variations in optics, grips, and other attachments. It can be altered to perform well in practically any situation, which is why I would prefer the AR configuration.
The AK is a solid style platform wether it be older soviet AK-47s or newer style 7.62x39mm AKM platforms or even AK-74/AK-100 series of rifles chambered in 5.45x39mm the AK definitely puts up a fight. Of course the AR is a quite well sealed system so jams might not be quite as common as people say but an AR kept unmaintenanced will suffer greatly in combat aspects, of course AKs hardly ever jam and most likely never will the right type of ammunition (such as types that won't cause squib loads or similar problems involving powder and prime). A straight out of the box AR will most likely best an AKM chambered in 7.62x39mm due to the ARs 20" barrel
And the AK only coming straight from manufacturing with a 16" barrel but an AK with a 20" barrel will do just as well if not better. 5.45mm platform AK rifles would probably be close to the accuracy of an AR straight from the manufacturer because the lighter weight and less recoil caused by the smaller 5.45 load. It's true the AR can be customized with optics and grips and other accessories which do help a lot whilst shooting but fancy attachments don't mean anything if the gun doesn't fire, the 5.56 round also is pretty low rcoil especially in a semi automatic rifle. Rails can be obtained for older AK platforms with no rails for the right price such as railed dust covers are made for AKMs. In short the AK and AR have there pros and cons and in order to find the right rifle you would need a lot of option weighing and fact analyzing.
The AR/M16 is a scalpel. Just like the AK is a hatchet. You don't use a hatchet for delicate situations and you don't go chopping trees down with a scalpel. If I'm a SWAT guy and I'm door-kicking in urban areas, I'm grabbing and AR, If I'm a poor freedom fighter and I don't have money for parts and I don't care about over penetration, I'm grabbing an AK.
Although, one could come to a complete functional compromise and get a 5.56 piston driven upper and another 6.8 piston driven upper. Just switch when necessary, and you have the functionality of both.