I agree with slug. When I was talking about my feelings about large families, I was careful to say 'very large families' because I'm not talking about 5 or 6 but 9, 10 or 11 - at which point it becomes very, very hard to provide each child with sufficient parental input. Again, I'm not saying it can't be done - but it is obvious it would need a very special parent to do it.
My mum is the eldest of 11 and feels that her childhood was entirely swallowed up with caring for young siblings. For her, the company of those siblings is not a consolation - she feels as though her mother basically abandoned her.
Her youngest brother - my uncle, who is my age - was bullied and scapegoated throughout his childhood. Children hunting in a pack is not a pretty sight, and there was insufficient parental supervision to control that.
My gran often tells me, "It gets much easier after the first four!" but I think she can only mean easier for HER, and that is because by then you have an oldest child who can start taking over. She also tells me that they all got individual time, but sometimes only by getting children out of bed for bathtime...
It is difficult to discuss this without stereotyping, and I do think some really disagreeable things get said to and about large families that I wouldn't want to ally myself with. And I am NOT saying large families = crap families, because of course that is very far from true. But in everything we do, it is easy to do a good job if you have sufficient resources. And large families generally have less in the way of resources. So the larger the family, the more skilled the parent has to be to maximise the positives and mitigate the drawbacks.