I believe it will depend on the dog. There is no guarantee with either coming first how they will get along. Of course with the exception that Dobermansrule said "she will be the boss!" LOL With my girl, Kyrah, there are only about 3 dogs she really gets along with and seems to really like. She has no mothering instincts or loving instints (cuddling, licking etc...) towards other dogs. I am hoping maybe as she get older? I can hope anyway. She does like to play with puppies but after play she is done with them. Get away and give me my space!From my experience, I'd say a male first. Nina has not taken too kindly the boys we've brought in that were younger than her. She has 0 mothering instinct, and rather gets nervous and anxious.
I'd say a boy first, then a girl. No matter what a boy will ALWAYS love a girl. The girls get set in their ways, and seem to find the boys intrusive...especially obnoxious puppy boys!