Originally Posted by
neuroanatomist
Depending on what you do, having a backup body or a second body to use both at once may make a lot of sense.
For me, it makes less sense to have $ tied up in a second body. I expect I can live without the 1D X for a couple of weeks if necessary, when I travel I only take one body anyway (and if it were to die, I'd just buy a Rebel to finish the trip).
As for the 'reach advantage' of the 7D, IMO the 5DIII trumps it. At low ISO, an image from the 5DIII or 1D X cropped to the FoV of the 7D has equivalent IQ - if 8.5 (or 7) MP is enough for your use (prints up to ~16x24"), you're giving nothing up. At higher ISO (over 800) the IQ of the cropped FF image is better. Also, with the f/8 AF of the 1D X and 5DIII (in April), in many cases you can add a TC to your lens, meaning less cropping of the FF image and even better IQ.
Finally, the AF of the 5DIII (and 1D X) is more consistently accurate than the 7D.
At this point, I personally see no need for my 7D...