I always viewed the Constitution class being slightly larger, with its lower hull, as having more space, more storage, giving it a greater range. Kind of like a Cruiser; whereas the Miranda didnít have the lower hull, its range was lesser, would have to pull into ports more often, or require some kind of supply line. Another words, the Constitution could be used for missions requiring them to operate independently for longer periods of time, like deep space exploration. And the Miranda, would be used for operations closer to home, like border patrol, or assisting in colonizationís, science studies, etc. The Constellation, with its four nacelles; and still no lower hull; well speed for internal operations.