There is a reason that all militaries use FMJ ammo. The "Rules of War" asside, they gain a consitancy in feeding and better penetration against hard or hardened targets.
While SP ammo may have a better effect upon hitting someone, it is not reliable if you must shoot through a barrier, even a light one. If in this type of situation, it is not likely that someone will becomming at you in the open. Stupid on their part if they do.
Some AK rounds do tumble after impact, but stay togethter for the most part. The wound is not that much greater than a FMJ round passing through the body.
The Yugo FMJ does tend to come apart, but are you willing an able to clean for corrosivness in a SHTF situation? Most are not.
If you are looking fo simple, reliable effecvtive ammo, go woth Wolf, Barnaul, or Uly FMJ.
I get the best accuracy with Barnaul folowed by Uly. Uly comes in Spam cans as does Wolf now.
Both Wolf and Barnaul use the "newer" type of bullet that yaws more quickly. Not sure about the Uly.
In reality, no one wants to get shot. People argue for days over the best round to use, but in the end, any hole through the body will make most people stop what they are doing or run away right then and there. That is all you really care about.
Any Ak round will put that hole in someone and defeat thin barriers in doing so.
Have some good SP ammo around in case you need it, but for the rest, just stick with what the military uses. They have a reason for doing so.
Hope this helps.