It's a tough question that we have struggled with with both our kids. At the end we've reached the conclusion that we need to balance between the needs of the child and the needs of the parent.
The first 2 months after the birth we were both home, then my wife stayed for another 9 months & finally I took 1 more month of parental leave (so in total it was 1 year before starting to acclimate him to daycare).
After almost a year at home my wife needed (mentally & socially) to return to work & if we could afford to live off of her salary alone I think I would have gladly stayed at home for another 6+ months (instead of just 1).
But I don't think our kids would have been better off overall if my wife stayed for another 2 years but would have done so only out of a feeling of obligation and suffering during that time (it is VERY isolating to be a stay at home parent, even when you have contact to other parents of young children & there is a real lack of intellectual stimulation despite there constantly being work to do).
I don't have all the answers but I think it's a tough question & the balance really depends on the kids and the parents - I believe there is no "1 size fits all" solution.