It depends. While research from the National Library of Medicine does show that water flossing may be more effective in fighting gum disease, and is better for reaching periodontal pockets and plaque, the argument is really about which method you’ll actually do.  If you don’t enjoy water flossing, you won’t reach for the water flosser and consequently, won’t floss at all. So, the best method is the method that you’ll be most consistent with.