In addition to what Pete said, there's the ongoing advantage of having the thermostat exposed to a small amount of circulating water as the engine warms up rather than heating stagnant water under the thermostat by convection only. On my 235, I had a problem of the temp. guage swinging almost into the red zone before the thermostat would open, after I drilled the 1/8" hole in the flange, as soon as the engine reaches operating temperature, it stays right there.
