I personally think it depends a lot on your playstyle. The biggest question will probably be whether the AK or the M9 is better because of the subtle differences with each. However, my personal suggestion would be to have a GMAL loadout, an AK loadout, an M9 loadout, and a Dragon Sniper loadout to allow you to quickly switch to adapt to different situations in a map. And plus, if you alternate between them, you'll develop a taste for them yourself. Not to mention, if you wind up not liking one, you can just substitute it wit the FAL. I don't really think any gun is OP or broken or anything like that, and I haven't since the game came out.
While admittedly, I've barely ever used the AK-47 (I currently have 2 GMAL loadouts, a Dragon one, and an M9 one), the appeal is there. Each gun is better for different situations, but which of the 3 is best overall is something I can't tell you. While I use the GMAL most, that by no means makes it the best adapted gun of the group as I haven't used the AK enough to judge it.
So yeah, to summarize that, I think they're all equal (hell, all 5 long guns in terms of effectiveness) and that the only way to find which one is the best (for you) is to continually try them all. Plus, it helps when you run out of ammo and have to pickup somebody else's gun.
Edit: I realized after typing this that I'd completely forgotten about the KAL, which I never use or plan on using on account of believing it to actually be the worst of them overall for anything but being incredibly close. So yeah, my advice would be not to try it because you're defenseless if you're trying to survive against someone scoping on you from a bit away.
--- ( PSN: L-W-X ) "In our world, every storm has an end...Every night, brings a new morning."