I sold my 6D (before the 6Dii was announced), bought an 80D as a stop-gap measure. The extra focus points on the 6Dii are a little too bunched up for my liking. So I am still on the fence about what FF to buy.
I don't think the 6Dii offers enough to tempt me into buying one, and the IQ of the 6D/6Dii is such that the 5diii is not much of a contender. So I have shortlisted the 5DIV - pretty much has all that I would want. Just waiting & keeping my eye on the prices.
IMO I don't think the technology is that new in the 6Dii, most of it has been on other recent Canon bodies as well. There is nothing to "prove", Canon cameras usually work fine/reliable - to me it is items like focus points/FPS/DR etc etc that will sway choice.
The 5Diii is a great camera but I would rather hold out for the 5Div - it is little things like anti-flicker (which I find excellent!) that have pushed me away from the 5Diii!
Also ,you have a nice range of L lenses so budget for you doesn't seem to be a (major?) constraint.
Happy shopping to you!
Canon 80D, 700D & G7 X; EF-S 10-18/18-135 STM, EF-S 18-135 IS USM, 50 F1.4, 100 F2.8L Macro, 16-35 F4L, 70-200 F4L IS; 100-400 L II, Speedlite 430EX II