I owned a 7D I then bought a 5DIII. Kept the 7D as a backup. It just sat in the bag.
Fast forward about a year and a half. I needed to learn something about video. Began with the 5DIII. Then, bought a refurbished 70D at a good price. If I need to shoot video, I use the 70D -- flip screen, touch screen follow focus, 18-135mm STM optimized for video.
Now, fast forward another eight months. I needed to start shooting sports for a client. I found a 7DII at a good price. Now, I consistently use the 7DII when shooting sports (or birds, when I'm shooting for myself – which has become a rare occurrence) and the 5D III for everything else.
My opinion, the 5DIII still holds a slight edge in overall quality and the sensor is more forgiving when conditions are less than idea. But, the 7DII significantly narrowed the gap.
So, I'm embarrassed to admit I own three bodies:
5DIII – the all around workhorse. Suitable for 90% of shooting situations. If you need to shoot in low-light this is the preferred option.
7DII -- the budget 1 Dx for sports and birds. Tolerates cropping and pushing significantly better than the original 7D. At higher ISOs the images look "grainy" (like film) not "noisy" (like electronics), which is a much more pleasing look in my opinion.
70D -- budget video option that punches well above its price point. For me personally, I've found video work has not been as much in demand as my stills shooting, so the 70D isn't getting much of a workout.
Bottom line – any DSLR today will produce excellent images under 90% of conditions. It's that other 10% that should drive your purchases. I bought the 7DII because I'm spending 50% or more of my time living in that 10% where I need high frame rate, fast, flexible auto focus and decent high ISO performance. Conversely, I need the 5DIII because probably another 30-40% of my time is spent is conditions where I need to be able to produce publishable images shot in poorly lit rooms, where flash is not an option.
Note that my personal situation is that in the past year I went from shooting 90-95% for myself to now shooting 90-95% for others. If I were just shooting for myself, I would only need the 5DIII. And, if were wealthy, I could buy a 1Dx and longer lenses and not need two bodies.