Light Gary.
Both are equally strong, but when they're gasping for their last breath, Light Gary has more friends to come save him. It is only statistically though. Something like 53/52. The difference being someone's great grandmother not thinking much of Dark Gary generel appearance.
Once again Light Gary is saved by decades old fashion advice.
Light is emitted through energy
Entropy guarantees energy will one day run out
No matter how long light shines on a place, darkness is waiting to pounce as soon as the energy dies
The only thing faster than the speed of light is the speed of darkness
Darkness knows that the Light is a candle burning away and patience will see the heat death of the universe wrapped in Darkness. The end will see no Light. Whatever remains will wander alone, forever in the Dark.