American Bulldog temperament

The American Bulldog is a guarding breed. This breed is sometimes wary of strangers, and can exhibit shyness when meeting new people. The American Bulldog is typically a happy, friendly dog who does well as a family pet. Like many other breeds of this size, the American Bulldog requires plenty of exercise and mental stimulation.
 

Boxer temperament

Boxers are energetic, playful dogs who are typically very active. They are very friendly and social dogs.

From the AKC breed standard, www.akc.org

“These are of paramount importance in the Boxer. Instinctively a hearing guard dog, his bearing is alert, dignified, and self-assured. In the show ring his behavior should exhibit constrained animation. With family and friends, his temperament is fundamentally playful, yet patient and stoical with children. Deliberate and wary with strangers, he will exhibit curiosity, but, most importantly, fearless courage if threatened. However, he responds promptly to friendly overtures honestly rendered. His intelligence, loyal affection, and tractability to discipline make him a highly desirable companion. Any evidence of shyness, or lack of dignity or alertness, should be severely penalized.”