I'm following this tutorial on how to control Raspberry Pi GPIO pins with Python scripts. Instead of connecting the test circuit (LED + resistor) between the ground and the GPIO pin however, they connect it between the +3v pin and GPIO (see section 4, last paragraph). The author says this is to have the current come from the 3v pin rather than the GPIO pin. However, from my limited understanding of electricity, the magnitude of the current through the GPIO pin should be the same regardless of how the polarity has been set, the only difference would be its direction.
Am I wrong about the current? Is it actually better to draw power from the 3v pin instead of the GPIO pin?