I think there's no doubt that parents can really mess you up, but I remain to be convinced that it's better for unhappy parents to split.
I work with troubled teens and none of them live with both their parents. Now, of course, a lot of their issues stem from the horrors they witnessed before the split and those children, although damaged are still better off than they would have been if they'd stayed.
However, we don't see kids traumatised from living with unhappy but together parents.
We do see a lot of kids letting their parents believe they love the new blended family or only seeing dad at weekends, or having two bedrooms/sets of belongings who are in fact broken by it inside.
I think this is an important area for research but atm it's not popular to suggest kids needs both parents at home, so there's no real will to do the research properly.
I was part of a very small scale and unscientific study on teenage suicide. Although actually far too large. Our LA had seen a shocking 17 suicides in years 9-13 in a period of 18 months and schools were under pressure to find out what they should be doing differently to prevent it. Without any additional funding or resources they set about trying to establish any links between the tragic children.
Among the 17 children there was a real mixture of popular and not so popular, academic and struggling, sporty and not, poor and affluent. The only things they all (every single one of the 17!) had in common were some previous self harm and that their parents had split and both parents were very much still involved. The children were spending significant time with both parents in apparently successful and amicable arrangements.
Now, of course, the correlation doesn't prove cause and there's a lot more work to be done. Very many children live in these kinds of arrangements and don't commit suicide but it is a significant pattern worthy of further research that won't be funded because it would be politically unpopular.
I know from my other work that children are often not as happy as they appear to be about having two bedrooms, no matter how lovely they are and that even in the most amicable arrangements children do feel very torn and disloyal to one parent or the other.