Age of the children, living conditions, and ability to support the children are usually the biggest criteria. If the children are over a certain age (depending on state law), they may be allowed to decide where they want to live. But in most states, the mother is still preferred unless there are documented mental or physical health problems.

The courts favor any parent who does "churchy" things with their children. Take them to church even if you can't stand going to church. It's not right... but that is how the courts play the game.

It is not all about the "best interests of the children." I have been fighting custody for three years, and we have been to coparenting counseling, mediations, and through 3 custody evaluations. In all three evaluations, the children's message was clear; they wanted more time with mom. Even the mediator called the sperm donor an "ass" and commented that was all financiallly motivated for him (so he didn't have to pay child support). In spite of this, it all comes down to one thing. It is simply about what each parent has a right to. In the end, that is all the courts weigh in the decision. I am a Sunday School teacher and teacher in the public schools. The sperm donor does not attend church. The attorneys say they consider moral upbringing in all the decisions. That's bull! The fact that I take them to church plays no part. They will not even allow me to ask the sperm donor to take them to church his weeks, because they claim the courts can't enforce it. He was sleeping with the other woman in a one-bedroom apt before we were officially even separated, and I had to allow the kids to go and spend nights with him and that tramp. The only thing courts consider is what stands in the way of a 50/50 custody arrangement. I have been their primary caretaker their whole lives. He left when they were 2 and 4. They are now 6 and 8. Joint custody is the standard and courts will not settle the argument until I agree to let him take my kids away from me fifty percent of the time. Apparently each parent has a right to the children fifty percent of the time, even if up til the divorce they were only there 10% of the time. Our son has medical and psychological issues; constant care and stable environment are paramount for him to be well-adjusted. To the courts, that doesn't matter. "Dad has a right to the kids fifty percent of the time," so even if it is NOT in the best interest of the kids, we must flip/flop them every other week. The laws need a major upheaval.

Gender of the parent.

As sad as it is, taking them to church does not matter one bit. Each parent has a right to the children fifty percent of the time. Moral upbringing, what's in their best interest, etc. has little to no impact on the custody decision.

the looser?

Who has the vagina is the main criteria. If both parties have them then its up in the air, the same as if neither parties have them.