I think you can find a dog that fits your criteria in either line. I met one dog from the showline breeder you mentioned above and it's a great dog, good temperament, solid nerves, and the owners socialized him very well. I don't know anything about the breeder since I haven't met him/her but the dog itself is great and the owners are very happy. I'm not recommending them because I don't know them, I'm simply telling you my experience with one dog from them.
If you're willing to travel to the Cornwall area, perhaps touchbase base with Shade on here. She got her working line pup "Delgado" from Stalworth and would likely be willing to chat with you.
Jazz, Shiloh Shepherd, 5 yrs old, CGC HIC
Bunny, GSD X, 7.5 years old
Last edited by fuzzybunny; 11-20-2012 at 12:31 PM.