Female dogs do not necessarily make better pets. However, they do tend to mature faster than male dogs and intact females may be less aggressive and difficult than intact males.
Differences between males and females are usually fairly small in spayed or neutered animals. Their faster maturity can make females easier to train than males, especially when the dog is younger. However, females also tend to be more independent, which can make them a challenge to train. They also tend to be less forgiving of mistakes made by both humans and other dogs.
Male dogs can be more aggressive than female dogs. This often takes the form of threatening behavior, which may not lead to an actual attack. When female dogs do attack another dog, it tends to be a more serious fight rather than a display. Male dogs are more likely to bite people than female dogs, although the cause matters. Resource guarding, which is aggression in an effort to protect food or another valuable item, is the same in both sexes.
Intact female dogs can be difficult during their heat cycles. These cycles, which mimic pregnancy in a hormonal sense, can cause the dog to develop anxiety or protectiveness. She may be more likely to attack people or animals that startle or her approach her possessions, such as a favorite bed or toy. Spaying alleviates this problem.