When I look through the industry magazines gear reviews and products for the new year, somehow nearly every paddle blade looks the same - teardrop shaped. There's only a few on the market which are shaped differently, mainly for the purpose of reduced shoulder/elbow strain and more control in paddling. I use the Werner Nitro and love the narrow width blade. Next on my wish list is the Ottertail designed by both Infinity Surf and Werner Paddles.
Much like the ottertail blades in canoeing, the shape allows you to vary the depth of the blade in the water thus creating more or less power and/or control depending on what you're doing. Steve Boehne of Infinity has been shaping surfboards since the mid 1960's and his two sons assist in design (and testing) bringing years of experience to the table. Product link: Here.