The only thing that saves this question is the word more, of course. I totally agree with both the previous posters, but neither of them is particularly practical. We probably shouldn't expect them to be, as they're teenagers and they've just fallen in some kind of love. They do have to turn to adults to help them conspire to be together, and both of them do that (Nurse and Friar). These adults don't really help them be practical, either. All the plans the adults have are flawed, and the most practical suggestion of all comes from the nurse who advises Juliet to move on with her life and marry Paris (which would, of course, have been illegal). Juliet does seek out the advice of these two adults, and they let her down. I guess I'm the "hard-hearted Hannah" who looks at Romeo and Juliet as a tragedy more than a romance (in fact, I just saw a local production of it "on the green" last night, so the tragic wastefulness of it all is pretty fresh in my mind) and am always struck by the incompetence of the adults in this couple's lives. Given that, Juliet seems almost amazingly practical.
I agree with the first post. We are assuming in your question that you are asking who is more practical: Romeo OR Juliet?
Certainly, when you consider basic social trends in teenaged boys and girls, you see that girls tend to have and show more maturity at a younger age than boys. Certainly this trend was not lost on Shakespeare. In most of his plays, he seeks to promote the inner-strength and intelligence of women. This play is no different.
In addition to what the first answer said, I'd also add this. In addition to desiring to make her mother and father happy, when she realizes they are not going to see things from her point of view, Juliet seeks the wise counsel of more than one adult to advise her. When the nurse fails her and tells her (essentially) not to be true to her heart, she goes to the friar (a priest, basically).
Put this into today's perspective for a moment. How many teenagers, when unable to talk their own parents are seeking the counsel of other ADULTS before anyone else? Most that I know go straight to friends. Not only is she asking adults for counsel, but the first is a woman who knows her well and loves her, the second is a religious man who knows and loves Romeo. I think this action alone shows her to be practical - and mature.
I agree with akannan, but would offer a few additions, based on considering Shakespeare as a man of the theatre.
It would have been highly unusual, theatrically, for the young female character (referred to as the ingenue) to be headstrong and independent. Young female characters in Shakespeare's theatrical world were conventionally dutiful and obedient. If you know Shakespeare's play Much Ado About Nothing, you'll see what I'm talking about, if you consider the ingenue character, Hero, as compared to the unconventional character of Beatrice. So, Shakespeare has taken a very young female ingenue in this play (R&J) and given her all the headstrong valor usually reserved for the young male lead.
Romeo, on the other hand, employs much flowery language, and, in the text his speeches convey many of the attributes of a typical ingenue. An especially interesting comparison between Romeo and Juliet is the different ways they approach the Friar for help later in the play. The Friar must chastise Romeo ("Art thou a man?") and works hard to convince him to come out of hiding and face his banishment. Juliet, on the other hand, runs into the Friar's cell brandishing a knife and threatening to kill herself rather than marry Paris. This just after she has endured one of the most intense scenes of the play, in which her father tells her to "beg, starve, die in the streets."
What is interesting theatrically to consider is that, in Shakespeare's company of actors, both of these characters would have been played by young men -- young men very close in age to each other. Almost interchangeable! This gives some frame of reference when one ponders where the heck Shakespeare got the idea to have his female ingenue be full of fight and logic, while making his young male lead softer in nature and full of flowery language.
If the actors could be interchangeable, why not the qualities of the characters they play? And so might the very innovative characters of Romeo and Juliet have been born.
Given the fact that both of them are seen as "star crossed lovers" and both of them have become so interlinked with the basic idea of all-consuming passion, it's hard to see either of them as practical. Yet, I am going to go with Juliet for this one. I think that she is fairly mature for her years. To me, she seems to be the more practical one of the two. It has always been my impression that Romeo comes across as rather whiny and ambivalent at the start of the play. He seems to be more obsessed with his own predicament than that of establishing a union of two souls with another. His first interaction with Juliet was one where I sense a "rebound" element present. Yet, Juliet is really quite pragmatic. She is fairly dutiful as a daughter and is one who uses the power of reason to ask to the Nurse about his identity. She understands the implications of being from warring families better than he does and is really good at developing the plans that both of them follow. I find that her question of "Dost thou love me," is really a practical move. I am not sure if this is how it was intended to be perceived, but I really like how she pins down, only figuratively speaking, Romeo. It seems that she knows how the temperament of men might be and for her to boldly, at fourteen, to call out whether or not he is going to be able to commit to her is really pragmatic. I guess my view is motivated at my feeling that Romeo is not the strongest of the two. Juliet proved herself to be far more practical and resourceful than Romeo, in my mind. I encourage you to go into the text and look at her character and her lines. I think you will find that she speaks and embodies more elements of pragmatism and practicality far more than Romeo.
Juliet, she tends to be the more practical person. She tends to think about the consequences of their actions and is careful of their actions. Like after their marriage and Romeo is in Juliets room, just before dawn. It is juliet who sends Romeo away, otherwise they would be caught.