I have two AR type rifles, and several AK's. If I would need a rifle for any kind of defensive work, (SHTF) I would grab one of my AK's.
In my opinion, the AK is like the Glock of rifles. It is simple, and just plain works. The 7.62 x 39 I believe is also a better cartridge.
If you shoot an AK enough, and get used to it, I think the ergonomics are really quite good.
This is subject to much debate, but it is what works for me.
That being said, the AR's surely are a cool weapon, enjoyable to shoot, and fun to customize.