Compact armored warship or large space cruiser?

Is a very large space dreadnought better than a more compact armored ship at the same speed?

The compact ship is preferable for fighting, but a long-range mission may require the larger hull's endurance and stores.

For the proposed space battle, the preference is a smaller, heavily armored ship. It presents a more difficult target, and the thermal argument favors a hull that is easier to keep warm while radiating unwanted heat. A long-range voyage creates a different requirement because the ship must carry more expendable stores. The preferred size therefore changes with the mission's demands.