I have both the 7D and the 7dii. I had the 7D for nearly a year and the 7Dii was supposed to be an upgrade for me.
Both cameras were set to the same exact settings (or as close as possible given that the shutter speeds have slight variations, etc.). I was shooting horse races using both the 70-200mm f/2.8 L IS II and the 3oomm f/2.8 L IS prime lens. On day one I used the 7D and 7Dii with the 70-200 lens alternating cameras one race after the other. On day two I alternated cameras race by race using the 300mm. RESULTS: Both the 7D and 7Dii shot identical quality shots using the 70-200mm. Using the 300mm prime lens, only the 7D shot in-focus shots one after the other. Nearly every shot taken by the 7dii was blurry. I spent a solid week testing and retesting. Same results.
There is something inherently wrong with here. Compatibility issues? Maybe? I sent the 7Dii back to B+H which honored their 30-day return policy.
Now my search for an upgrade to the 7D continues. I thought the 7Dii would be that upgrade but it turned out to be a huge disappointment!