I have to say that is quite impressive.
It appears better than my 6D and in a different league to my 7Dii although I don't have scooter to do direct comparisons.
Do you prefer lightroom for raw processing over canon dpp?
Short answer: I'd expect you'd see a solid 1 stop high ISO improvement vs your 6D.
My perspective: 7D (mark 1), 60D, 80D, 5D3 and 5D4.
The full frame sensors should have about 1 stop of high ISO noise advantage over APS-C, due to the fact they have over twice the surface area.
The more recent Canon sensors (probably starting around the 7Dii) have much better noise character - so even if they were not quantitatively better, qualitatively the noise is less objectionable.
For me, the 7D (mark 1) and 60D were good at 1600, just about ok with a decent exposure at 3200, and ISO 6400 was a last resort. In comparison, I'd judge the 80D as nearly 1 stop better (for my personal taste).
It's the same story with the 5D3 vs the 5D4. ISO 3200 was fine on the 5D3, with 6400 being OK. 12800 was usable, but pushing your luck. For me, the 5D4 is (for practical purposes) 1 stop better, and even ISO 25600 is usable.
I have prints from the 5D3 at ISO 25600, but the gap between the 5D3 and 5D4 at this setting is quite remarkable. From what I've seen, the 5D4 is closer to the 1Dx2 than the 5D3.