So I am set on getting myself a 15mm lens for my Elan 7e and I am stuck at a cross roads. My other two lenses are Canons (50mm and 20-35mm). However! The 15mm Canon EF lens is something like $589 at BHphoto, while the Sigma 15mm is new on ebay for $389. I've gone to all the reviews on here and they all say either "This Canon lens is great" or "This Sigma lens is just as good as a Canon," so now I turn to you . What do you guys say? They are both f2.8, but is the Sigma really as sharp? Is the money savings so good I can't pass it up? What do you think I should do? Any and all input is appreciated. Thanks! -Justin