I think they're both about tied for me. Both have a lot of impact when watching them. There are different aspects of both that I like as well, so it's hard to draw a line.

I do have to say that I much prefer Watsuki's art style to Kishimoto's.

EDIT: whoah...I didn't even notice that I had already posted in this thing. Meh, bumping 6 month old topics does that to ya'.