I feel the need to put my two pennies worth in here, since I figure I am fairly well qualified to do so.
My mother was 19 when she had me, 21 when she had my middle sister, and 36 when she had my youngest sister. I was 41 when I had my daughter and that was no accident.
My parents were far, far better parents to my youngest sister than they were to me and my middle sister. They were cruel (beatings with 'the slipper') to us, but never to the youngest; they never allowed us to use the phone to speak to friends because it was a corded one on top of the television and God forbid we should interrupt my father's viewing of the news, but by the time our youngest was of an age where she might want to phone friends, they had a cordless one which she happily took up to her bedroom and spent hours talking on. They flatly refused to collect my middle sister and I from any evenings out with friends, so that if we wanted to go out, we had to walk there and back alone over country fields sometimes at midnight. Not once would they ever have refused our youngest sister. Our mother was also a little jealous of us when we were teenagers - she used to put us down all the time and never had a nice word to say about anything we wore - she never did that with the youngest. These are just examples - there are plenty more things I could cite.
Neither of us are jealous of our youngest sister, btw - actually, our parents would probably have had a fight on their hands if they'd treated the youngest in the same way they did us (and we were old enough to collect the youngest from nights out ourselves etc etc if they'd refused anyway).
I saw the difference in parenting and that is one of the reasons I had my daughter 'late' - because I thought I would be a better mother. Actually, having had parenting like I did, I would never, never have repeated it anyway, but for someone who hasn't seen the two extremes close up, then I'd say I definitely come down on the side of the older parent (in general) to be a more patient parent, and one without his/her own issues to deal with alongside raising a child.
So there. 