Hi,
l have used the 7D and the 5D Mk 1 and now have a 5D Mk3, and would have to disagree with our friend who reccomends the 5D Mk 2, and in fact I rate the 7D and 70D much higher than either of the earlier 5 models, though have not used a 6D so cannot comment on that.
My reasons are quite simple. I.E. The 5D Mk 1 was a wonderful camera for image quallity but the autofocus was lousy (And I do speak as a very seasoned Pro photographer). The 5D Mk 2 offered even better image quallity but sadly used exactly the same AF system, so again was a very poor camera for action photography, whereas the 7D is ultra fast and quite brilliant.
Hence Canon learned all of these lessons and incorporated them in the 5D Mk 3, which has even bettered the 7D's Auto focus performance and on full frame as well, and much of this AF technology has also been incorporated in the smaller sensor 70D as well. Certainly I would go for the 70D as a cheaper second body to my 5D Mk 3 now in preference even to my 7D.
Hope this helps, Don Morley
