Concur with what fal308 said.
The AK design is an example of Eastern military theory: Make it cheap and simple, easy to mass produce, and reliable. Soviet troops weren't trained in semi-auto marksmanship. Their battle theory was
-artillery keeps their heads down
-tanks take out their tanks
-armored personnel carriers roll up a few hundred yards distant
-infantry unloads and keeps their heads down in final assault fire (basically spraying full-auto at them in the final rush) until they are close enough where they can't miss. I mean like jump in the same foxhole range.
If you hadn't guessed, Eastern thought emphasizes mass and the whole rather than the individual.
Also, the AK is an example of an assault, or intermediate power cartridge. More powerful than a handgun round (used in submachineguns in WW2) but less powerful than a full power rifle round. In the Russian example the 7.62x39 and 5.45xsomething are less powerful than the 7.62x54 in their Mosin-Nagant WW1 design rifle and more powerful than whatever they shot in their PPsh-41 burp guns.
The FAL is a perfect example of a Western military thought battle rifle:
-powerful enough to nail any enemy soldier you can see and then some
-more expensive to manufacture
-designed for soldiers trained in individual semi-auto marksmanship.
So, battle rifle vs. assault rifle?
Eastern vs. Western?
I personally prefer Western rifles. I can't help it. I think like an individual.
As to Battle rifle vs. Assault Rifle:
If you fight at ranges under 25 yards, the assault rifle has an edge. Between 25 and maybe 100 they're about equal. (I'm guessing here) At extended ranges or through hard cover, the battle rifle has an edge.
There are other factors: If you have to carry 500 rounds of assault rifle ammo and 500 of battle rifle ammo, guess which weighs more???
Hope that helps.