I like AK but I haven't convinced myself to own one yet. I already have an M4 that serves as my sporting rifle and MBR. But the AK simply looks bad ass.

If I buy an AK, that means I will have to add another caliber to my roster which at this point I am trying to simplify. I have already invested thousands of rounds of my existing calibers (pistols, rifle and shotgun). Mixing an AK round to my current arsenal will just add to confusion when an actual SHTF/WROL breaks out I also don't want a caliber converted frankenrifle. No confidence in using one.

The only justification I have to get an AK is affordability.
If I have to choose between the two, what would be best - Izhmash AK-47(Romanian) or Century Arms AK-74 (Bulgarian)?

What would the advantages between those two as far as: customization, ammo/parts availability and ammo price?

Will an AK be a good sporting rifle as opposed to an M4? I know training will solve that but what's your take?