We're all biologically pre-programmed with a circadian rhythm that causes a reduction in body temperature and cortisol levels, but an increase in growth hormone and melatonin production during the night hours. This allows for a more restful and deeper period of sleep. And I think there's been comparisons showing that those that sleep at night feel more rested than those that get the same amount of sleep in the day, but I can't find exact studies right now.
However, light is the primary cue in controlling circadian rhythm, so if one is especially careful about finding a very dark place to sleep in the day, sleep might be just as restful as if it were night. Even a slight presence of an intense light source, like the sun, will cause cortisol levels to rise and disrupt the correct hormonal balance that occurs in night-time sleep.
So I voted for the third option. Our bodies have evolved such that they expect a period of low-activity during the night when it is best to recover and repair from a day's worth of activities. And so it's night that will provide the most natural and convenient way to get more restful sleep, which we know helps with gaining muscle. Most people could probably eventually adjust well to sleeping in the day so long as they find someplace dark for themselves.