I suggest choosing based on the angle of view that you want. If 200 is long enough for most of the shots you want on your 7D, go for the 200mm f/2. If it isn't the 300mm f/2.8 will be a better choice. Of course, you can put a 1.4X on the 200mm and get a 280mm f/2.8, but I wouldn't suggest relying on that as a matter of course for sports.