I have seem quite a bit about sleep, and every study seems to come out the same way, night sleep is better.
If you have to work nights they suggest creating a dark bedroom to help your body not react to light of the day (not sure if it helps).
There is a link to quality and what time of day, some Docs think humans are design to sleep at night and our subsystems recognize what time it is, no matter what we do.
Interesting stuff though.
_________________________
Undefeated in all of Asia!