I think the distinction is Google has specifically said they won't correlate Google Public DNS data for targeting advertising [1], while Comcast is specifically

I think the distinction is Google has specifically said they won't correlate Google Public DNS data for targeting advertising [1], while Comcast is specifically saying that's exactly what they do want the option to do. If you don't trust either company, that distinction won't matter. But if you take their statements at face value, there is a difference. [1] https://en.m.wikipedia.org/wiki/Google_Public_DNS#Privacy https://en.m.wikipedia.org/wiki/Google_Public_DNS#Privacy