Ok great i figured the image quality wouldn't be an issue. Its more of a control/button configuration. Just the overall feel of each camera type of thing. Would it just be easier to have 2 of the same bodies?
Well, that's sure. The 5D has a lot of buttons on the left side of the LCD, while the 6D has none. And it has not a dedicated WB button at all, so there are some differences that could slow you down a bit, at first. When I started using the MKIII, coming from a MKII, my right thumb was always searching for the zoom on the right top of the camera (which I think is a much better positioning, BTW...).
Im getting the same reaction when using my 5DMK3 as im used to the 7D config.. Being i will be using 2 bodies and you have to have reflexes like a cat in a wedding. I dont think the seconds it will take fiddling and checking which camera u have up to your eye or hitting the wrong button is worth missing "The Shot" again easier shoot with the same bodies.. but that isnt EASY on my pockets.. lol