Between Romeo and Juliet whose love is more passionate and how?

Though Romeo and Juliet are quite infatuated with one another, I would say that Romeo is more passionate about Juliet than she is about him. Let's consider the circumstances for the titular characters at the open of Romeo and Juliet. Romeo is heartbroken and listless because Rosaline does not return his affections. We learn that Romeo is "in love with love," and wishes to be so. Juliet, on the other hand, is not really interested in love, but certainly does not care to be married to the man her mother is planning for her to meet.

When Romeo and Juliet meet, I think that they are falling in love with the idea of one another rather than the people they are. The two hardly speak more than a handful of words to one another—though physically attracted to each other—when they begin kissing and wooing! Juliet is quick to be in love because it provides an alternate to her mother's arranged marriage- maybe she can marry Romeo instead! (At this point, she does not know he is a Montague.) Romeo is perhaps quicker to fall in love—entranced by Juliet's beauty, Rosaline is entirely pushed from his mind.

It may sound harsh, but I think that Romeo and Juliet are using one another. It is difficult to say whether they manipulate each other, but they definitely exploit their perceptions of each other to achieve their own desires. Who's to say whether their love was genuine? If they did not truly love one another, they must have loved the idea of each other because they were willing to become married and even commit suicide rather than face a life "out of love" or in an undesired marriage.

Regardless of whether any manipulation or using occurred, I think that Romeo was more passionate in his affections for Juliet or the idea of her. Consider the famous balcony scene of Act II, Scene II. When Romeo speaks of Juliet (to himself) he goes on and on about how she is more beautiful than the moon, as beautiful as an angel, and how he wishes to stroke her cheek. In contrast, Juliet (speaking to herself) only ho-hums that she wishes Romeo was not a Montague. Even when the two begin to address each other directly, Romeo seems to not care that Juliet is a Capulet, but he does feel sorrow that he is a Montague and her sworn enemy. Couldn't he just as easily be angry at her for having been born a Capulet?

Later, in Scenes III and V of Act II, we can sense this difference in passions when Romeo and Juliet speak of each other to their confidantes. In Scene III, Romeo has come to Friar Laurence to ask him to marry him to Juliet. Fair Juliet, who he professes to love with all his heart, and who he is certain he really loves and wants to be with. When Juliet speaks to Nurse, she is all business. She does not speak so fondly of Romeo and instead plainly asks whether he had anything to say about their marriage. Even with her most trusted friend, Juliet has the opportunity to gush about how much she likes and loved Romeo, but she doesn't. 

To me, it seems that Juliet is really only in love with the prospect of being married and taken away from her mother's designs on Paris as a husband. Romeo, at least, focuses his love on Juliet as a part of being "in love."