Sooner or Later-Which is better for the kids?

It seems that these days, everyone's parents are either already divorced or heading towards one.  There also seems to be two trends with divorces.  They either occur when kids are very young, or when all the kids have graduated and are going onto college.  Both ways have their pros and cons.  If parents divorce when kids are young, they won't understand as well what is going on.  Sure, they'll be upset, but there won't be as much anger and resentment from very young children.  However,  then when the kids are growing up, they won't have both parents around in the same home to support them.  It makes things more difficult in terms of custody issues and working out time so that both parents can be involved in the child's life.  On the other hand,  waiting until kids are out of the house allows so that both parents can be around while the kids grow up.  However, if there is tension in the house and the only reason a couple is staying together is for the kids, it'll create some serious issues.  What do you think is the better option?