I've owned & used all 3 (but only the Eotech & PK-AS on AK's).
PK-AS:
Pros: Extremely rugged, reticle usable in most situations w/o battery power (a good thing in case of circuitry/battery/switch failure), less expensive than the others, circle/dot reticle great for both precision shooting & CQB snapshots, integral QD mount, excellent FOV/SA. Irons instantly usable w/the PK-AS since it sits offset to the left so not much cheek/chinweld (w/the bore-centered PK-AS-V you have to remove the optic first).
Cons: Can be difficult to sight in (but you only have to do it once), the PK-AS-V sits very high, has eye relief (which makes eye distance/position important), short battery life. The only functional/reliability problem I've ever heard of w/the PK-AS is the dot dying w/o known reason or cure (not terribly frequent but the only one I've heard of). Black reticle can be slower to use/pick up (YMMV).
Eotech:
Pros: Great FOV/SA, combat-proven, the 512 uses common/rechargeable AA batteries, good battery life, circle/dot reticle great for both precision shooting & CQB snapshots, less expensive than the Aimpoint, comes w/integral mount.
Cons: Some find the circle/dot reticle "too busy" (YMMV), useless if batteries/circuitry/switches fail, sits very high, adjustment buttons are slower/more difficult to use.
Aimpoint:
Pros: Combat proven, exceptional battery life, brightness control faster/easier to use, sits lower than the Eotech but not as low as the offset PK-AS, some find the single dot faster/easier to use than circle/dot reticles (YMMV).
Cons: Most expensive of the three, doesn't come w/a mount (which makes it even more expensive). Useless if batteries/circuitry/switches fail for any reason.
With that being said, I use the new Aimpoint CompM4 on my PS90's. On a SAR-1 I would choose either the PK-AS or the Kobra -03 (think no-frills Eotech w/multiple reticles which uses AA batteries) since both are made for the AK and come w/integral QD mounts unless you want to spend $300-$700 on a combat optic for your SAR-1. HTH...
Tomac