EPA for each visit

In addition to the favours, they each give differing economy items scaling with your stats. Assuming 230 in each base stat:

Repentant Forger gives (Base Shadowy) x Cryptic Clue = 4.6E

Regretful Soldier gives (Base Dangerous + 50) x Whispered Hint + (Base Dangerous + 50) x Rat on a String = 5.6E

Sardonic Music-Hall Singer gives (Base Persuasive * 1.5) x Whispered Hint = 3.45E

Wry Functionary gives (Base Watchful) x Cryptic Clue = 4.6E

If you don't need specific favours, definitely visit the Regretful Soldier. He's also the best for low stat characters, because part of his reward is independent of your stats.