All i was saying is the difference between Crop and Full Frame reach is Minimal, Same thing with Extenders and my point was why waste the money on it. Again, when i went from my 70D to the 6D, I was shocked at the difference in reach, It's was literally nothing. Go Full Frame and never look back, just my two cents.
I guess I'm a bit confused. You see virtually no difference when shooting your 300 f/4L on the 70D and your new 6D? If my math is correct, the field of view would be quite a bit different, i.e., about 180mm different.
Perhaps, the subject matter has to taken into account. My intention is not to correct you. It's just that I concentrate on wildlife, especially birds. It might matter more to me than to you.