Are single stack 9mm and .380 ACP guns still relevant in the world of compact double stack guns?

I say yes… availability, price, reliability, and size of single stacks make them still viable. At close range, self defense distance, they will still stop a threat- but do your homework, try many guns, shoot them, see what feels good to you, what’s reliable, and what you can shoot accurately. A big gun is great, but if you can’t hit your target with it, it’s no hood.