The German dogs have different ratings in shows. SG -- Sehr Gut or Very Good, is the best rating a puppy can be awarded in a conformation event. V -- is excellent. (Not going to strain my German), and VA is Excellent Select. These ratings are given out at the sieger show in Germany.
In order to be shown, the dogs must attain at least a schutzhund 1 for their first Sieger show, and I think SchHIII for their second. Not sure if that is the same for bitches. They must complete an endurance test, and perform protection work at the show to be considered. Dogs that score poorly on the protection might be pulled from the show because they would then be put at the end of the line of dogs.
VA dogs will be selected and there may be only as many as they will consider VA, that may be eight or twelve more or less. Dogs are also judged by their progeny group, their ability to reproduce themselves or produce other excellent dogs.
A German showline dogs pedigree should have VA dogs as well as V dogs.
A German workingline pedigree will be more likely to have V dogs in it and SG dogs. While conformation is not the emphasis in their breeding except how it affects their working ability, they still produce excellent dogs in conformation, and then tend to scoff at the VA dogs as being substandard in working traits, having an extreme topline (ie the fiendish roach back), and having weaker nerves.
And the showline fanciers tend to diss the working lines for having insane drives and energy, and straighter top lines, and any number of other complaints.
I like the German showline dogs. My current dogs are mostly German Show and American lines. I have two young bitches with some working lines in them that I will never breed. I have had two dogs with some working lines in them, and they are not my cup of tea. But other people prefer them over all others.
I think you can have junk in either line, and you can have gems in either line.
Find a couple of excellent breeders, and let them sell you on their puppies. Look at pedigrees, look at what they are doing with their dogs, particularly the dogs they are breeding, look at health screenings they perform, and look at the knowledge and integrity of the breeder. With a good breeder, you can get an awesome dog out of German show, German working, East German DDR, Czech, and even American lines.
So you really have to decide what dogs are most pleasing to you, temperament first, and then all the rest. Look for the whole package, not just looks or color, or lines.
Lastly, the VA1 dog/bitch is called the World Sieger/Siegerin and would be similar to AKC Grand Victor/Victrix for the year. Only our GVs do not need the health screenings, titles, progeny group, endurance test, protection work that the Sieger/siegerin would need to be chosen. Also, I believe the class sizes at the Sieger show are much larger than the American Specialty National show, though they no doubt have ways to narrow down their overall grouping.