this just in: personal skill makes ship balance very hard to argue on an anecdotal basis
(I mean, except for battleships.)
but objectively, the Coalition gunboat is pretty solid. It fires six of its seven guns forward, five of them back, and five? to either side. I think the only issue is that it only fires four up and down, so you have to stay level with your target. It had moderate levels of armor and turn last I checked, so it should be about average in fights.
