This is quite amusing. Husband n wife may have their problems n decide not to continue w the marriage. But the child is innocent. If parents truly love the child, they shd be fair n think for the child. The child's opinion shd be respected, as to which parent does the child want to stay w. Unless either spouse is a morally bad eg for the child, then maybe tat parent shd spend less time w the child. Otherwise, the child shd be allowed to enjoy the love n care from both parents in order to grow up healthily.
Custody issues shd be discussed w the lawyer. Honestly speaking, husband n wife shd contain their own unhappiness n not spill over to the child. Think from the child's viewpt - who would want to stay 3days in a house n 4days in another house? There is no sense of belonging at all. Rules n discipline will be diff in both houses tat makes it confusing for the child. The environment, clothes, room layout etc will all be different. Pls dun make the divorce more challenging for the child.