Deciding when to Spay or Neuter
As you may have discovered, there are many different opinions from vets and breeders. For health and development reasons there is evidence that supports waiting until the dog has reached maturity. Since in German Shepherds don’t fully mature until they are between 30 and 36 months, this may be older than you would probably want to wait. Besides bleeding all over the house for weeks while she prepares and is in heat, If she accidentally gets pregnant before she is spayed then you have an issue with getting rid of the puppies and her nipples will never fully go back to their previous state. This is probably the main reason for the push of spaying at 6 months. Once they go into heat you will be surprised at how strong mother nature is.
You will probably want to have females spayed before she turns a year if simply to avoid the whole going into heat mess, however if you think you can deal with the mess and keep her away from other dogs (as well as keeping other dogs from jumping through your screen window to get to her…), then there may be slight advantages for her in waiting another year.
There may be advantages to waiting in males as well in order to allow their development to occur properly.
Below is a link to a great article that discusses pros and cons of waiting;