As an active duty Army officer with two tours in Baghdad, Iraq, I say go for the AR. I own a Stag Arms one myself. The nice thing about them is all the accessories. Once you have a lower you can get lots of different uppers with longer barrels for accuracy, shorter for combat shooting, and there are tons of weapon lights, sights(I like EoTech and ACOG personally--very different designs, but both good in their own right), bipods, etc, etc. They are fun to shoot, accurate, kick very little, fire as fast as you can squeeze the trigger on semi if you have it clean and lubed and use good brass ammo, and if you reload, the . 223 is real cheap.
If you want a play around rifle to fire that you never clean, the AK is your best bet. They can be made accurate but are not as nice a weapon. Or, just go with an SKS. I have one of these also and it is super reliable and will fire every type of ammo I have put in it no problem. I think it has been cleaned once or twice since my dad brought it back from Vietnam as a war trophy...