SKS gets my vote. It has a ton more stopping power over the 9mm even with self defense ammo. If you can't stop someone or something with 10 rounds out of that rifle then you really have problems. If 10 rounds isn't enough load up another clip. Ammo is cheap and easy to find for both. Also, I personally think an SKS is more fun to shoot and truck guns often come out as plinker guns at the range.