Juliet's love is more intense. I would have a difficult time choosing between the two of them if Romeo wasn't lamenting over his uninterested love, Rosaline, in Act 1, Scene 1. Juliet is not Romeo's first love, so that "first time" amazingness of love does not apply to Romeo. I'm a bit of cynic when it comes to Romeo, since within the same day he goes from professing his love to Rosaline to doing the same thing with Juliet. That doesn't scream passionate and intense to me. It says fickle.
Juliet, on the other hand, goes from a girl without a serious thought of love and marriage, to falling hard for Romeo. It's clear that Juliet's relationship with her parents is a good one. Her father is not forcing her to marry (at least not in Act 1), her mother gives her advice and Juliet promises to keep it in mind. It appears that Juliet really does honor her parents. After she falls in love with Romeo, though, her affections are so deeply passionate and intense that she defies her parents. She also contemplates suicide if she cannot be with Romeo. Juliet risks so much more for Romeo than he risks for her in return. For those reasons, I believe that Juliet's love is more passionate and intense.