I am not putting down the camera, just saying that it is not for me as the difference between FF and this is vast. And since it will always be like that I will continue using FF till I can afford to. I believe now that the only reason to go crop is budget.
IQ and budget are not the only reasons people consider this body; many pros employ a 5D3 and 7D (now 7D2). With the buffer and FPS on the 7D2, there is simply nothing comparable in the class/price range...
5D3: 6.1fps, buffer maxes out at 18 frames
6D: 4.5fps, buffer maxes out at 16 frames
7D2: 10 fps, buffer maxes out 31 RAW frames!!
In three seconds of shooting on a 5D3 you've taken 18 shots and maxed your buffer - you get almost twice the shots on a 7D2 in the same time frame (not to mention the extra reach of crop). It's pretty astounding when you think about it.
If you're not trying to capture the shot of an eagle grabbing a fish from the river, or the hockey puck entering the net, the baseball player swinging past the ball at the plate, or the race car driver making that amazing pass on the track, then the 7D2 is probably not for you. It is simply a specific tool for a specific purpose; one where both the 6D and 5D cannot measure up.
However, I'm rather irritated about the vast differences in sharpness between the models, for example the 60d looks very blurry vs. 70d/7d2 and the 6d is a lot shaper than all. Is this because of lens properties, aa filter, or... ?
This is the nature of pixel density and FF vs. crop sensors. Crop sensors cram more pixels into a smaller area. Think about it, the 7D2 has the same MP as the 6D and 5D3, with a sensor that is almost half the size. Even the 1D series employed a 1.3x crop APS-H sensor for a number of versions. Hence, the photosites on these crop bodies are smaller resulting in noisier (or "blurrier," as you call it) images. Canon, and all camera manufacturers have worked diligently over the years to improve the quality of crop sensors, and they have made great strides. But physics is physics, and you can only do so much with so much light, in such a small area.