I had long chat with a lady yesterday who is toying with the idea of whether to have a puppy or a rescue dog.
I hope I wasn't biased, being a breeder but this is what we discussed.
A puppy comes as a clean canvas. It will have no bad habits and what it learns will be up to you. If training is started from day one, is correct and consistent then the resulting dog will be what you have created.
It will be very accepting of your life ie children, other pets, routine and life style.
A rescue dog is unknown and whilst it is very sad that they are in need of a new home they are an unknown. They will have had the all important ground work done and who knows how well.
They will inevitably be more "set in their ways" and have routines. That being said many go onto new homes and bring great joy but many don't. It is a gamble!