CloudFlare, which offers a medium scale CDN and familar to the crytp-currency world as the company that asks visitors to fill various captchas on crypto-exchanges and similar portals.

OpenDNS, Google DNS, Quad9 etc are other players in the market.

Personally I was a fan of OpenDNS and never uses Google DNS as such. After the Cisco Acquition of OpenDNS their "neutrality" was questionable. But then there was DNSCrypt which made the DNS queries safe and I continuied to use OpenDNS.

But it seems Google had managed to strech its reach and use DNS as yet another area for its full dominance of the web and internet. Arguably they can't and they don't use DNS data for targetting. (ie as per their policy.)

Cloudflare on the other hand started as a small outlet, a garage startup few years ago and has done some amazing work in the area of internet security and speeding up things in general.

Its seems offering a DNS will indirectly benefit cloudflare by sticking to its mission and vision of speeding up internet. In the process their customer's portal will also get a speed boost if end users are using 1.1.1.1

What is DNS ?

For the end user, DNS is invisible. But when we enter a domain name in the browser, the operating system uses "DNS" to find the physical location in the internet / network of the domain. Needless to say, DNS resolution should happen in milli seconds.

If you are interested, here is a good article : https://computer.howstuffworks.com/internet/basics/internet-infrastructure8.htm

For example, I use Quad9 DNS and it takes 127 msec to resolve my domain freebird.in

The cloudflare DNS takes few milliseconds less than that

;; Query time: 114 msec
;; SERVER: 1.1.1.1#53(1.1.1.1)
;; WHEN: Wed Apr 04 19:34:04 IST 2018
;; MSG SIZE  rcvd: 72

So ClouFlare seems to have a faster experience.

When should one change DNS ?

Its always a good idea to use a faster DNS than the one which ISP provides as it tends to be very slow and also in many cases ISPs abuse the users by collecting and passing on the date to advertisers. (Needless to say, ALWAYS to Law).

So its always a good idea to use a DNS service like CloudFlare or Quad9.

CloudDNS is good for general purposes and instructions are here : https://1.1.1.1/

Quad9 DNS is little slower but provider malware detection and the details are here : https://www.quad9.net/#Setup_Quad91

Which DNS for families and Kids ?

Though there are many commercial alternatives https://cleanbrowsing.org/ is a Non-Profit oriented trustworthy alternative.

Does it really matter ?

Yes - never USE the ISP provided DNS! Further its based on your need use, a service like CloudFlare, Quad9 etc.

If you are in an area with internet survilliance and censorship, Cloudflare offers a service with DNS over HTTP.

what do I use ?

Well, I use Quad9 for testing for now otherwise its a DNScrypt enabled provider.

In terms of speed, for now CloudFlare's new serive tops the list as per various surveys.