Juniors are almost without exception male. Although some daughters are named after their father or mother, very few have exactly the same first name as one of their parents. Boys, however, are frequently named after their fathers - named exactly the same.
This practice, meant to honor the child's father, is typically a matter of pride for the entire family. Problems, however, can arise when the individuality of the son is not sufficiently recognized. Although their names may be the same, a father and son can be drastically different from one another. If the son is expected to copy not only his father's name, but also his actions, accomplishments, or opinions, parents will become disappointed and the child frustrated or even resentful.
Also consider what name your son will go by everyday; because there will be two people (or more) of the same name in the house, your son could be addressed by a variation of his father's name (Dave, Davey, David; basically whatever the father doesn't go by), or as Junior. Although nicknames generally strengthen a person's sense of self and their social skills, the nicknames of Juniors may prove troublesome since they could imply that their holder has a lesser name than his father; hence, is less of a person.
The major tip about Juniors: Although naming your child after his father can form a special bond and respect between the father and son, do not measure your son against his namesake.