In the early game where I don't have a high trade bonus from dip tech, it's not difficult to work out if the -10% 'malus' to your home trade node's income from collecting from that trade node makes more money than the amount that would made from transferring it instead.
I generally find that assuming a -50% trade power malus to collecting in a trade node that isn't my home node gives a good estimation of what the impact of both merchant actions will be. This doesn't work later on in the game, but by then most players have control of the home trade anyway (at which point it's a meaningless question).
I generally find that assuming a -50% trade power malus to collecting in a trade node that isn't my home node gives a good estimation of what the impact of both merchant actions will be. This doesn't work later on in the game, but by then most players have control of the home trade anyway (at which point it's a meaningless question).