Just to put in my two cents. The main things to consider are:
- What lenses do you plan to use? Fullframe: go with 5d
- The 5d is more sturdy (more of the casing is metal) and the mechanical parts are rated for a lot more exposures. Do you need this?
I have no fullframe lenses and take less than 10000 photos a year, so I'd go with the 6d, and spent what I saved on good lenses. Good lenses, cheap camera > cheap lenses, good camera