I'm going to give you a bit of advice...slow down. Live in the NOW. You're not just worried about this dog, you're now thinking about the next one? You haven't even trained a dog to do any of the things that will be required of it in Schutzhund and you're already making decisions on how a dog will be or won't be.
How old is your current GSD? Why don't you take her to Schutzhund training and see what its all about. It's a HUGE commitment. It's wonderful to talk about, its wonderful to think you have the time for it, but when you really start doing it, you realize how much you have to sacrifice and sometimes people just aren't ready to make that sacrifice.
Sorry...but in a matter of 30 minutes, after one post, and after what I'm assuming is some research on the internet, you went from thinking about one of three breeds, to settling for one. Slow down. Go to clubs. See the dogs work. Talk to people that know and can explain the differences to you objectively (the internet is terrible at objectivity).