So... how are you basing the idea that one type of space-faring craft is more 'realistic' than another? We don't have any real ships meant for interstellar flight and combat, and in space, giant balls of thrusters and guns would be the most 'efficient' ship designs, as they'd be able to move without having to turn.
Technically speaking, the 'Wall of Death' and 'Cube of Death' is just as realistic as any other. There's no reason for space-only craft to be streamlined.
