My parents split up when I was 6. My dad's a bit of a sexist dick, so I think it was for the best for me. Possibly not for my brother. But it was a really, harsh upbringing, with a lot of poverty and little opportunity most of the time. And while there's a lot about the break up that was good for my mother, I think she might have had an easier life over all if she hadn't had to struggle so much for 14 years while we were growing up. She wrecked her health trying to make things great for my brother and me and now we've left she's a bit of a shell of the woman she was and doesn't have the resources to do the things she used to want to. I think she might have been better off staying with him (if he would have stayed), but it's hard to say really. Would depend on how he behaved I guess.
I was one of only two people in my year with divorced parents growing up, but more than half my friends' parents broke up within 5 years of us all leaving school. Several of these I've been told were a matter of staying together for the kids, I assume most of the others were too. Some friends were aware their parents were unhappy, others were not. They all have mixed feelings on their childhoods.
I think the idea of some kind of league table re: damage to kids from an unhappy marriage or from a divorce is a bit of a crappy way of looking at it. Situations are mixed. Some things will be better. Some things will be worse. The way that impacts you will depend on all sorts of things, including what you're thinking about as having needed. Poverty can have a drastic impact on kids, but if you're poor because of a divorce, you probably don't attribute the impact of that to the divorce, you may not even notice the way it lowers your life chances, because that's the nature of that type of disadvantage, you never know what in particular would have been different for you.