@aryary,
There are many more factors that just those two.
And a child's choice is given varying degrees of weight, depending on the age and maturity of the child, and the circumstances of the case. For example, many children would like to stay with the parent that does not make them do chores, or who does not have a curfew, or who buys them the most/best presents, but that does not mean it is in the best interests of the child to be placed primarily with that parent.