That depends on the resistor you're using to the tip120.... is the tip120 a transistor? base collector emitter? vs a fet?
a fet has a high impedance, and only takes a small amount of voltage to switch on, where as a tip120 relies on current and without a resistor you could be damaging your pin out on the arduino. with a fet you'd need a pull down or the small capacitance keeps the led's on...