But are the Romulan colonies puny, or are the population and resources more evenly distributed? I don't think there's an answer in canon, but I picture it as reasonably well distributed.
The interesting thing is, we don't know whether the UFP is any better distributed as such. We know it consists of more than one homeworld, but we have only seen glimpses of two that appear to be harsh wastelands that pose serious problems even to their native (?) inhabitants - Vulcan and Andor. And we never saw a colony that amounted to anything much. The biggest on screen so far is Deneva, a well-established, at least century-old "former freight hub" that only had "almost a million" inhabitants, and could go silent for a full year before Starfleet paid any attention.