.....As for which 7.62x39 ammo is more effective, many of the cheaper commercial Russian hollowpoints have less than impressive expansion, and generally functions similar to FMJ ammo. But some of the higher-end HPs function well, like the Hornady SST. Among the cheaper 7.62x39 ammo, the soft point round is often a better choice for expansion/"stopping power".
Also, be sure to test the HP or SP ammo before you buy a large amount. Many AKs and SKSs have issues feeding anything other than FMJ.