Both my boys are Feb birthdays.
I didn't defer either of them.
For DS1 his first school was tiny - 26 in the whole school, 2 others in P1 who were girls nearly 10 months older. He got an inferiority complex, assumed he was stupid and spent most of his day under his table rather than sitting at it - his dad and I were going through a breakup, so he had that to contend with as well.
When I moved in May to a bigger school they found he had hardly learnt anything and we ended up keeping him back so he redid P1 at the new school. He's never looked back and is now in S1 in the top stream for Maths and getting good reports. I certainly don't see any issues that were highlighted by that report in the news on deferred children.
DS2 is 4 years younger and was desparate to join his big brother at school, so I didn't defer.
He's the youngest in his class (27th Feb birthday), but tall for his age, so the only problem I've really had was when his teachers didn't know he was that young and thought his behaviour more childish than it was iykwim.
Socially he does prefer it when he's in a composite class with the year below as he has more children closer to his age (as deferring seems to be the 'in' thing), but academically he's not had any issues and is in the top stream for Maths.
So I'd say it depends on your child. How ready do you think your son is? Does he go to nursery and if so what is their opinion on his readiness?