This breed is a very popular kind of dog. It's also a large-size breed, highly intelligent, super confident, and energetic. The most common color for the dog is a mix of brown/black/light brown/red. They have strong jaws with a scissor-like bite, big erect ears, and a long bushy tail. Most have a straight back, however there are dogs with a sloped back. This isn't very healthy and can impede the dog's gait and give him issues in his hind legs later in life.
Considered to be a highly intelligent breed, they pick up quickly to new tricks and commands. Because they are so easy to train, they are often used as police dogs, guard dogs, search & rescue dogs, and labor dogs. They are very loyal and bond well with their owner, so it's no wonder Hewie is so quick to accompany Fiona and protect her.
Other than its color, the dog is not different than a normal Shepherd. Basically, it comes down to personal preference. It is seen as more exotic and rare.