Stuck on whether or not you should get a girl or boy dog all depends on your personality and the maintenance that comes with either gender. There are a few significant differences then there would be between either dog of the same sex; all dogs have different personalities. There are a few differences in taking care of a girl dog, like when they are in heat and if you breed them.
Some people believe that girl dogs are more protective and aggressive when it comes to her pups and the family, this is not always true but may be more apparent in certain breeds. It comes down to a matter of maintenance with a female, if you choose not to breed you will need to prevent visits to the park or having her around other male dogs. If you are looking to breed, there will be significant changes in your home and how you take care of a dog and her puppies. If you are hoping to have a low maintenance dog, then spaying is your best option. Female dogs tend to mature faster and are smaller than boy dogs. This sometimes is a better preface to training and how quick they learn desired behaviors.
Male dogs in certain breeds can be more stubborn, but this again is not true across the board, and every dog has a personality of their own! But it is true that male dogs grow slower than females and also tend to mature later, so they grow at a different rate than a female dog.
Depending on your environment and the amount of time you have to take care of a dog can be the final decision in which dog you decide to get. If you don’t care either way, then deciding will be that much easier!