@jellofishxo I think it also really depends on the trend in your area. I held my August child and she will start Kinder later this year the week she turns 6. But in my area holding a kid is very common, many of the kids in her “young fives” class have May, June or July birthdays. So we were concerned there would not have been many or any kids her age and a lot of her classmates would be over a year older than her.
FWIW, her cousin who is a month older started kinder so we split them into different grades. I actually saw this as a positive, though, because I hope it will reduce competition and comparison, especially when it comes time for college applications, etc… (My extended family can be very competitive. My husband and I are not.)
We looked at it as giving her one more year of childhood, and maybe most importantly more time to mature before middle school. My husband and I were both kind of late bloomers, and my daughter was seeming the same way to us. (I still wanted to play games and pretend when my friends were all getting interested in boys and other tween stuff.)
A lot of parents in our area also hold their boys for athletics, because they have a better chance of making it onto teams if they’re on the older end.
My daughter also had a tough year of pre-K with a lot of older girls (early birthdays) in her class, so we were wary of sending her straight to K.
We just finished school and have zero regrets about her “young fives” year. She has developed so much confidence this year and we are happy to be sending her to school without the hesitation we would have felt last year.
Good luck with your decision! Sounds like your son will do well either way!