I agree with George, both are very good. But I have to give my vote to the 70-200, I have experience with the f4 and f2.8 non IS version and they are a joy to use, you can control DOF wonderfully! And the make very good candid photography, because of the conversion factor on my digital rebel you can be in front of people several feet away and get great shots, without them being aware of you. If fashion and model photography is your main intrest I would go with the longer lens.