How do you compare the outcome for a kid who never exists? People are an end in themselves before considering any outcomes.
Catholics believe that the primary end of sex and marriage is procreation, albeit not ruling out secondary ends. That’s beside the point. People being an end in themselves means that before considering any outcomes of their lives their existence is good. E.g. if I have a kid who has Downs Syndrome their life is a fundamental good even though their outcome will probably be considerably worse than a healthy child. Many non-Catholics share this view. That does have implications for family size as it moves one’s attitude towards responsible generosity to having children rather than primarily considering the child a threat to or means to some other end.
Like some of my strongest memories are of leaving notes for my Mom about how I felt neglected and was in <x> room waiting for her just to BE there with me. She'd last about ten minutes before she'd begin multi-tasking. Not because she was a bad mom but because she just had so. much. to do with five kids and a full-time job.
If you're going to have a large family older kids have to take on some of the emotional labor or the younger kids are totally shafted.
Sometimes I see it phrased as older kids taking on some of the labor in what is perceived as maturity building activity that may serve them in adulthood.
Others use a completely different phrase, calling it "parentification" and then call it child abuse or worse, believing it's better for the kids to all fight for the resource of the parent rather than share the burden with older children.
I withhold a conclusion of what the results are. But it's funny to me to see how the opinions can be gamed based on how you frame it.
Running a family that large is also certainly more time consuming in some aspects- grocery shopping is a significantly different experience when you go through multiple gallons of milk and dozens of eggs every few days, as an example.
You rely on older children to help, and the whole family unit functions as a team.
A good friend has 8 siblings. My parents both had 6. I only have the one, who is several years older than me. The family dynamic between a small and large family is simply fundamentally different. That doesn't mean less emotionally attachable or available, but almost certainly less one-on-one time.