Typically I would not recommend a GSD as a "first" pup. However, that does not address your question.
My opinion is temperament, temperament, then health certifications. Have the parents hips been tested? Have they been tested for DM? (those test results are subjective from what I understand)
Read the stickies in the puppy section, There is a ton of information there.
GSDs are a lot of work as puppies, more so than a lot of other breeds. You have to commit to that for training for at least the first year.