This is a really interesting article, which looks at a Swedish study about sharing the care of children. Most of the evidence found that children do better if their care is shared between the parents.
There are always cases where shared care isn't an option, (for example where there has been violence) but it's clear children benefit from having two interested parents and shared residency supports this.
Divorce and separation can have a hugely detrimental impact on children. But Swedish studies show that having them live with each parent half the time is the best way to help them cope