I agree. The game is not long enough to make it viable to lower tax. You might run into a tipping over point late in teh game and have it make no difference - you'd have done better to get the money sooner and win sooner.

The problem is that 4 growth = about 0.8 - 1 koku per turn per city. The 10% is around 1/3 of the normal tax, which to me says something like 200+ per turn (600 taxed at normal rate is a low'ish amount in mid game, at low rate it would be about 400). You'd have to save up for quite a long time to make the gains equal. The problem would also be that your high wealth towns still also would have the low tax rate, and some of my provinces in late game have 5000 - 6000 wealth, giving me income of 2000 per town or so with Metsuke.