I'm finally ready to take the plunge from an AFD 80-200mm f/2.8 to either the 70-200mm f/2.8 VR II or f/4 VR III. Cost is not an issue, and I think size and weight isn't either, since I've been lugging the 80-200mm quite a bit around the world. My concern is the well known focus breathing issue, which seems to bring the f/2.8 closer to 135mm when set at 200mm for tight portraits. Anyone has done this and can provide an answer? I could go 1 of 2 ways: (1) buy the f/2.8 VR II used and try it out; or (2) avoid it altogether and get the f/4. Using it on D800. Thanks.