Which seems to suggest, at higher ISOs, you prefer the results you're seeing with DXO over what you see with C1 Pro? What in particular do you prefer?
More accurately, I find the automatic adjustment of noise reduction settings as a function of ISO superior when dealing with a set of images shot using auto ISO.
The noise reduction built-in DXO is also IMHO one of the best compromises available today.
I would need a huge amount of time to find the optimal noise reduction settings in C1 Pro to get close but I don't think I would reach the same quality anyway.