Firepower may sound simple, but actually it is NOT. Firepower means: the effectiveness of your ship's cannons.
Firepower may even be a personal thing; some people prefer heavy cannons with a long loading time to deal lot of Spike Power, but having a terrible Damage-Per-Second. So what's the best cannon weight (lb) for the most firepower?
You must ask yourself, what do I want to do?
This information is provided by the update that PotBS Wikia is undergoing, by Captain Vuur.