Should I buy from a breeder or adopt from a shelter?

I am confused about buying from a breeder vs adopting from a shelter. I am concerned with health issues (that most breeders test for) whereas shelter pups could run into some issues. It would break my heart to have to put down a puppy/dog for hip dysplasia very young...I have seen it as young as 2 years old. I felt that by finding a breeder that is very careful and does a lot of testing it would save me the heartache.Do shelters take the time to check out the pups nowadays?