In the long run I'd always go for the law bonus. It lowers corruption, thus you lose less money in that city. IMO the trade goods bonus of the temple of hermes will soon be eaten up by corruption and the need for bigger garrisons once a city has hit the 12000 mark. Plus your governors get this refined tastes trait thread more easily in Hermes cities and you don't want that.
Anyway, war has to feed itself I say, so conquer and loot. Good for the mens morale also...
Edit: damn, too slow
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