I should have wrote array of “entity” structs.

The reason I say ESC incurs more overhead is because I find it involves a whole bunch of access patterns to add, remove, update, and query the data. Comparatively arrays of entities mostly just involves basic loops.

Still a weird take, as the ECS approach makes it much easier to do AoS vs SoA which is actually great for access/loop performance.

I'm sure there's examples where a non-ECS approach beats out an ECS approach. But to say that ECS incurs more overhead generally is just plain false.

ECS are obviously more efficient for traversing a subset of your entity data if that subset resides in one small component, simply because the total span of bytes accessed is lower and the cache hit rate is higher.

I would be more inclined to claim the opposite: that ECS systems are generally MORE performant than arrays of entities, but you can really only be wrong when making general claims like that.