Why are Romulan warbirds so large?

Why do the Romulans build warbirds so large?

Their computer and control systems may require more physical space to provide the same breadth of functions achieved by more compact Federation automation.

One explanation for the Romulan warbird's size is that broad computing capability comes at the cost of physical volume. A Federation ship can be highly automated even with a large complement, while a Romulan design may need more hardware and supporting systems to perform comparable tasks. Apparent size may therefore reflect an engineering and automation tradeoff rather than superior combat power.