What age is perfect for our indie boys to be neutered?

I've talked to two vets and both suggested different ages; one said within 7-9 months while the other said it should be after 12 months. Kinda confused here.

I don't want to compromise on his bone or overall health. One dog owner even suggested that it's better to let them mate atleast 2 years prior the operation. They kind of scolded me when I mentioned the doctors' suggestions.