I have several issues with competitive parenting.
My dd1 was one of those who always achieved milestones early, picked up reading/writing early etc, and it WAS a bit tempting to feel a bit competitive about that. Then DS came along, and while I think he has a brilliant mind and am expecting great things from him one day, he is a bit of a square peg in a round hole at school and the comments I get from the teachers are less of the "reading at a 9yo level at age 6" and more of the "he can be very funny and it is SOMETIMES appropriate."
So, I realise it's not straightforward. And, I would not want my dcs to feel compared on overall ability. We let them read their own reports, but not each others, for that reason.
My other issue is that my parents put HUGE emphasis on academic achievement, and I felt a huge pressure not to disappoint them. Who knows, maybe I would have been like that anyway, but I'm conscious of not wanting dd1 to feel the way I did. I do praise her good reports, but I would like her to feel proud of herself, not just wait for the approval from me and DH. I had a frank conversation with her about that recently - she had been showing my mum some of her writing and Grandma apparently had shown it to a teacher friend, who said it was "above what would be expected for her age". DD reported this to me, and while I was happy that she was pleased with herself, I said that what other people say is not as important as how you feel you're doing yourself. Not totally sure I should have talked about that with her already (she is 10), but it's something I feel strongly about.