Preferably sunset; I am always awake for those. Nothing beats the sunrise after a long night of camping or tripping, just beautiful.
Tough question, on one hand a cold beer and a few friends talking while the sun sets on a summer night is hard to beat. On the other hand there's almost nothing that beats waking up in a tent on a chilly morning in early august, walking down to a nearby river and taking a bath in the ice-cold water and then letting the rising sun warm and dry your body as you watch the world around you slowly awakening. Ok, I'm picking sunrise!
i feel that sunsets are not more significant than sunrises, per se, but i feel that night makes everything more intense, more true, than day. i feel the same about night the way that most people feel about the day: it is a promise of a new beginning.