The steam ram traded gun power for speed and protection

Which warship type favoured speed and protection over firepower?

A steam ram. It emphasized speed and protection while sacrificing firepower, although the term was mainly American rather than a universal classification.

The question rearranges the familiar battleship and battlecruiser tradeoff. Battleships favour firepower and protection, while battlecruisers favour firepower and speed at the expense of protection. The remaining combination, speed and protection at the expense of firepower, is identified as the steam ram. That name was used chiefly in American terminology, so it should not be treated as a universal category.