CloudFlare doesn’t make their money off of brokering my attention, they have a decent track record of doing the ‘right’ things (or at least not the ‘wrong’ things), and they’ve made some decently pro-privacy statements in the past.
It seems that everyone wants to collect data on everything and figure out how to sell it off, so I’m not putting it out of the realm of possibility that CloudFlare could do shady stuff and abuse my privacy as well- but their general line of business doesn’t require it the way Google’s does.
All things otherwise equal, I’m gonna trust the company who’s business isn’t selling my profile a bit more for most things. I used to use Google DNS a lot, now I use CloudFlare’s. I trust them both more than Comcast, AT&T, and Verizon with respect to technical competency and security at the very least.