If you're concerned about the price of rounds, get the AK-74. Surplus 5.45x39 sells at $164.95 for 1080 rounds.

5.45x39 does have lower penetration but much larger cavitation and better tumbling performance than the 5.56.

There are *some* problems with century arms AKs in finish and quality(barrel alignment, trunnion alignment, sight alignment). Arsenal AKs tend to be the best out there although you have to pay extra. You may need a some sand paper though if you're obsessed with smoothness. Then slap it with Lithium Grease.

If you want a 5.56 AK, you can get the polish Archer(Beryl).

If you really want 7.62x39, it tends to shine when penetration is needed and you're preparing to fight in woodlands with heavy vegetation(Vietnam like). 5.56 and 5.45 tend to be deflect by leaves and wood. 7.62x39 AKs tend to have more variety in accessories(magazine & muzzle device).