Should I buy the 5D Mark III
Well David, I just bought my 5D Mark III, mainly because of it's low light ability and better AF system, and the dual cards was a bonus. The boost in frames per second was also a very nice upgrade. My 5D Mark II is going to my niece and I am keeping the 7D that I have.
There is only TWO reasons for me to keep the 7D which are the extra "reach" from the crop factor and the extra two frames per second (8fps vs 6fps) for when I shoot sports. Is the "reach" a biggie and the answer is "no" because I do have tele converters. The 8fps, is a bigger issue and something I need, especially at a race track, where 0.1 seconds is 20 feet of travel. If the 5D Mark III was pushing 8 frames per second, I would have dumped the 7D. Keep in mind, the 1D Mark II & Mark IIn which was a work horse camera did 8.2 frames per second and was considered a "sports PJ" camera and I consider 8 fps the sweet spot. I was seriously considering getting the 1D-X camera until the 5D Mark III was introduced. I think the 7D and 5DMarkIII make a good pair of cameras. There is just enough differences to justify them both.