Either for me. You how when you find a dog you KNOW you'll get no matter what, how you know he's your soul dog? Well, thats how I get my dogs, and thats how I always will. I do not automatically say I won't buy from a breeder or say that I won't buy from a humane society.
Frisk was bought from a breeder. He was from an accidental litter, and we raised him from 6 weeks. He behaives the best out of all three dogs.
Ethan was adopted from an organizated that rescues animals and puts them in foster homes, not pens all together. He came to us very timid, and he is dog aggressive, toy aggressive, and treat aggressive.... sometimes aggressive toward people.
Skylar was adopted by my sister from a humane society that kept thier dogs in kennels by each other, all exposed to each other. He came to us with many health problems (mange, intestinal infection, whip worms, and a few other problems). He is the most out-going best tempered dog we've ever had.

And like mentioned below, MANY shelters do not have a behaviorist. There are five or so shelters that are close to where I live, and I know for a fact that not a single one has a behaviorist. Maybe if they would have, Ethan wouldn't be so aggressive, or I would have at least been warned about it, but I don't care. Just because I wasn't informed of his issues, doesn't mean I will never adopt from them again.

Sorry if I got on anyones bad side, and I didn't mean any of this in any way to affend anyone.