Mediation is faster and less expensive but not possible in cases when one or both of the parents are being unreasonable. What are some of the common and less common risks to a child of 6 years of a case going to court, other than the money paid to lawyers? This is in the USA.
However you settle differences, be it through courts, mediation, handshake over coffee, the impacts to the child are mostly around a) how they see the parents interact, and b) if they get caught in the middle.
If you go to mediation, court, priest, yogi - unless the child is a witness how will it affect them if the outcome on the decision is the same? Mostly, the differences between the adults need to be settled between the adults. The child should not be involved!
The caveat to that is where the child is required to be involved, either because one parent feels the need to badmouth the other, or makes an accusation that requires investigation. In that case the child will suffer as they may often feel that they are being asked to pick which parent they love more, which is a terrible thing to do to them. If there is REAL cause for safety concern, then it is absolutely required, but if you want to stick your kid on the stand to tell a judge about how you are the better parent then.... you probably aren't. And hopefully a judge will know enough about parent alienation to nip that in the bud before the kid gets hurt.
I'm not sure if this quite answers what you are asking, but separation of a 6 year olds parents can be quite disrupting to he/she's life. When children grow up with the lack of both parents there at the same time, some psychological effects take place. There are multitudes of videos that you can watch on your own time on how it changes the kid's life, but I won't get in to it now because I don't even know if that is what you want to know. If the parents are dangerously unreasonable then actions should definitely be taken to protect the kid, but if the parents are not that unreasonable and can still provide a healthy environment for the kid to grow up, prosper and be educated, then it is most likely advisable to separate time 50-50 as best as possible. One must always keep in mind that the most important part in this process is not the dad or the mom (or whatever is happening), but it's the kid, for at that age, a kid is growing and learning the ways of life, and change as sudden and disruptive as that one can really take a heavy toll on its life. I hope this answered your question as best as possible.
The biggest risks to a child of divorce are psychological issues, primarily difficulty forming lasting relationships, later in life. Since the child doesn't know whether the divorce is settled through mediation or trial, that by itself doesn't seem likely to affect the child, though if mediation indicates that the parents have a better relationship, that might marginally benefit the child.
If you are the plaintiff, and your spouse did not want the divorce, the best thing you can do for the child is to suspend proceedings for a year or two, hire a good counselor, and make a genuine attempt to reconcile. If your spouse just wants more money, the best thing for the child is probably to swallow your pride and save the costs of a trial by giving your spouse a favorable settlement. Usually a trial is expensive enough that you can give a lot to the other party in a settlement and still come out ahead of where you would have been with a trial.
Not what you wanted to hear, I'm sure, but that's unfortunately how divorce works in the U.S.