[PvK]

Drones can be quite powerful, but they're pretty expensive to build up (like building an escort), and are automatically lost. I would tend to think they make sense to build up in peacetime and use to tip the scales by concentrating them on hard targets, but they may not be efficient compared to warships if built during a large-scale war. Drones are a good way to build up a lot of firepower without maintenance costs.

PD may not look like it's doing anything until a kill is scored, but it can be quite effective.

Missiles and torpedoes are not effective against drones because (Last I checked) they can't even hit drones.

PvK