Prime lenses tend to be sharper but if you are considering your camera makers top of the line lenses (like Canon's L series) there should not be a huge difference. What are you photographing most often that you are looking to a 35mm lens and which body sensor size, ie. full frame, 1.3 or 1.6 sensor? I personally want my investment in gear to give me variety and options. Granted my L lenses give me a F2.8 fixed instead of the 3.5-5.6 you are getting, so the speed gain is not as great. Keith
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