Speed and firepower in battlecruiser design

Which matters most when balancing speed, protection, and firepower in a warship design?

The mission decides. Reconnaissance favors speed, battlecruisers need speed and long-range firepower together, and close fighting favors battleship protection and subdivision.

The right balance depends on the ship's task. A reconnaissance vessel needs enough speed to gather information and escape. In the game example, three battlecruisers defeat a Russian pre-dreadnought by using superior speed to keep the engagement at long range. That tactic requires long-range guns with enough hitting power to damage the opponent quickly or disrupt its accurate return fire. Treaty restrictions are particularly troublesome when they limit the firepower needed to make this approach work. Close fighting, including the Baltic scenario described here, favors battleships with more subdivision and the protection it helps them carry.