Heavy gunships, cruisers, and fictional fleet choices

How might a heavy gunship differ from a heavy cruiser in a science-fiction game?

The gunship is bigger; the cruiser is the preferred choice for flexibility.

The gunship is treated as the larger option, while the cruiser is preferred for flexibility. Balanced task groups are the usual preference, but all-Battlestar fleets are also used in Battlestar Galactica: Deadlock. These are personal game choices rather than fixed definitions for real gunships and cruisers.