Assuming always that you go to a reputable breeder and select carefully, purebreds are more predictable in terms of what you're going to get.
We had two small children, so we went the predictable route with a Lab from a good show breeder. She is now almost 8 and a particularly Good Dog. We were so pleased with her, we got a second Lab, who is also a Good Dog but in rather a different way (she is a hot-rod field retriever, she's a very nice dog but quite a handful.)
I'm completely smitten with the working retrievers and wouldn't get a toy dog like the Griffon. If we did something other than a Lab (and I really see no good reason to switch) we'd get a Chessie. Great working dogs!
He was a good dog.
We have a Lab mix (looks like a Lab, but too tall and weighs 100 lbs); an Irish Terrier/ yellow Lab mix (hysterical when he stalks squirrels - he is BLONDE and the squirrels see him from when he walks out the back door) and a Cairn terrier/Yorkie mix (She terrifies the chipmunks). They have worked out their pecking order and generally tolerate each other,
There was a lady on the tube some years ago. I think her name was Barbara Woodhouse. Her mantra was ‘no bad dogs’.
She was right. Dogs become what we train them to be.
I am sometimes uncomfortable with folks who disparage American Staffordshire Terriers (I think that's the official name for pit bulls.) I've met some who are real mushes, and others that are nasty. But we could say the same about Yorkies or Poodles.
I guess it is just how we teach them to behave.
I've been owned by Chessies for over 20 years and they are wonderful dogs but definitely NOT for everyone. They're much different than labs - much more hard-headed...LOL - but I wouldn't own any other breed.