I imagine the true state of the art is pretty unbelievable right now. No way the current tech tree is actually stuck on 1990s quad copters with bombs strapped to them.
Their efficiency advantage drops quickly for diminishing sizes and weights.
That is why big birds use gliding whenever they can, but small birds and insects use almost only wing-powered flight.
Screw propellers are pretty much equivalent with wings whose rotation angle is not limited so they can rotate continuously around the body instead of having to reverse periodically the direction of rotation and the attack angles.