1% thank you for you fast and complete answer.
The main reason of thinking about an upgrade it was the full frame sensor.
After that , I agree with you and I know that in some cases like T2i and 7D for example ,we have the same sensor ...so the image quality will be pretty the same.All we got if we buy a 7D it's just some new buttons and additional functions (more or less essentials).
I'm not looking for additional options (loke GPS, WI-FI etc) I just want to find an upgrate solution to a full-frame with decent photo/video abilities and I have (at least in canon range) only a few options 5D MK2, 5D MK3 (price too high) and the new 6D.Actually as I've put in the post title 5D MK2 vs. 6D

It's not a rush ,I will try to make a video shoot mode comparation between cameras with APS-C sensor like T2i, T3i (DIGIC 4) ,T4i (Digic 5) even D7 (Dual Digic4) and the 6D (Digic 5+) FF sensor in order to see how big is the difference.
BMCC look so great, I just saw some movie samples, but as far as I understand , you can't use it in photo mode (hope i'm not wrong).
Best wishes,