Try and stay neutral. Don't say one single thing that favors one over the other, as they may very well repeat it in order to gain "points".
Divorce is nasty (although fortunately I haven't had one..but know plenty who have) so like it or not, they have forced you to quickly grow up on your own and you will have to make decisions that are best for you....not best for your parents.
Just try and weather the storm and appreciate the pain they are going through.