In space, does size matter?It makes sense to me that the Defiant would be relatively small. As long as they can support their weapons systems, a smaller ship is quicker to maneuver and accelerate and more effective.
WW II battleships were huge to make a stable platform for the big ship's guns that had range in many miles. Aircraft carriers were huge to make a useable flight deck. Now that guided missiles have much longer range than WW II guns as well as more accurate, the case for the battleship is gone. Galaxy classes are big for lots of science labs and a big crew to make a 5-year mission more tolerable, but they're not as good at fighting as a Defiant.