The thing is 10+ years ago ARs were EXPENSIVE and AKs were cheap. You could buy a AK plus 10 mags plus 2 cases of ammo plus ammo pouches for the price of a AR alone--and 556 ammo was expensive too. AKs are great guns (for what they are); but they've lost a few steps in the "tactical" rifle world. ARs are simply better, they are cheaper, they have much more aftermarket support and they are everywhere.

As for the 545 vs 762 option, its been long discussed that the 545 offers terminal ballistics based on velocity and the 762 based on mass. Maybe 545 is better; but in non steel core ammo, the 762 punches holes better. Clearly both are good killing rounds. As has been said prior, I think you will find 762 easier than 545, and likewise mags.

I think now, most of "us" think of the AK as a substandard fighting rifle choice, when ARs are available. Its not that AKs cant be GREAT rifles, its just that there are tons more that are simply marginal when compared to even entry level ARs. If you want a AK, then get a AK. If you want to fight with a AK, then do so; but don't be shocked when you see much better ARs