LWM confirmed that the Combat Mission Missouri is the best Credit Earning ship in the game.
The Combat Mission doesn't interact with flags. Instead it just throws a fistfull of money at you every time you play. While the "Best Game You Ever Played In Your Life" could result in less credits when fully flagged/bonus'd up because it was an extreme outlier, the rest of the matches you play are to the good. The Combat Mission at 30% meets and exceeds the payout from the Old Missouri additional credit modifier in almost all situations.