Hi,
Not sure how much this will help as i am not sure what you mainly photograph. I have a 5D11 and a 1DIII and although I have only had the 1D a few weeks I am already finding big differences.
After using full frame I found the 1.3 crop quite odd and I lost my instinctive close up framing of shots. On the plus side the extra reach is useful sometimes! I think both are wonderful cameras and have different qualities. If you want full frame then the 5D2 is a no brainer, if you need super fast AF and high shutter rate then its the 1D.
I love em both!
Dunc