If you have a very important event happening the next morning, it is much better to do everything earlier in that morning. Sometimes I have the tendency to do things the night before so that I feel like I can wake up at the last minute. But that is usually not much different if not worse to waking up a little earlier. The time spent is the same so the amount of sleep you get will be similar.
More importantly the mind is extremely fresh in the morning if sleep is adequate. This means that you would be more unlikely to miss something. It is also much easier to guarantee waking up earlier than being able to sleep in till later.