Working line people often think their dogs have the best structure. BUT the same goes for showline people. Even then, WGSL breeders prefer their own over ASL and vice versa (usually, not always).
I have seen a lot of WGSL dogs who can work and love to do so. I have also seen some ASL dogs who would shock you with how good they are at their work (one of our local k9 officers by my parents' is actually ASL).
If you go to a reputable breeder, they should be able to offer a dog with a stable temperament, at least fairly good conformation and a nice amount of drive.
Mom To~ Dakoda (b/t GSD), Acheron (black GSD)