I like boy dogs and will probably get another boy when I get another dog.
I know it's considered "safer" to get a male/female combo and I think, in general, it is. But I know my dog and he actually tends to get along with boys better, for the most part. I think as long as both are spayed/neutered at a proper age and socialized and brought up well, problems shouldn't arise. But females are known to fight worse.... boys scuffle, girls go out to kill each other, in my experience with dog fights. Girls also hold more grudges, lol. But I think it depends on the breed, too. Some breeds are more prone to same sex aggression.