I am using 1.1.1.1 and 1.0.0.1 for about 6 months now. It's very reliable but to really benefit from the DNS, you should set it in router settings.
I had problems with slow PS4 downloads earlier, but not since shifting to fibre optic connection. Google DNS is not safe as they use the traffic to target ads.
Akamai and other CDNs don't play nice with Cloudfare. For example, if you try to ping ax.itunes.apple.com using Google's DNS, you'll get an IP that's got pings lower than 80ms (on average, regardless of your ISP). If you use Cloudfare, it goes as high as 250ms. This is ONE CDN. Using C&W DNS would be better. Or even Level 3's resolvers would be better (since you connect to the UK/EU ones and pings to the UK/EU are around 160ms).
I get 112ms on 1.1.1.1 but 57ms on 8.8.8.8, but interestingly 1.1.1.1 resolves IPs faster and browsing (especially apps like reddit, instagram, etc) is faster.
That's a redherring regarding Google's DNS. They say on their website that they use anomymized query requests. There's no way they can use the DNS resolvers for serving ads. The only way they can serve ads is if there's a cookie on your computer and their websites have Google ads.
Secondly, I'm getting 30ms on 1.1.1.1 and 65ms on 8.8.8.8. Both resolve at the same time. Many ISPs here and services abroad tend to rely on Google's DNS servers (either as a primary source or a secondary backup).
So - in essence, two things:
1. the time it takes to ping the server matters - 160ms is slower than 60ms, but eyelids flashing is over 100ms (and that's pretty fast).
2. the time for the resolver to respond to your query matters (most public resolvers are fast anyway with huge caches).
3. the actual IP resolved matters the most (in conjunction with the above three). There's no point if a DNS server is redirecting you to a much farther away IP when a closer IP is available. And even Cloudfare's got servers within PTCL's network, the IPs they're giving aren't closer to us - but are closer to the Americans. BUT
4. Sometimes, the IP resolved (be it near or far) could have congestion on its route, but those are outliers since CDNs are supposed to alleviate that issue.
Changing your DNS servers matter significantly with CDNs. And most of the websites you access are hosted on CDNs. Even YTS Torrents. Or EZTV.
For me, this leaves out Cloudfare. It's either Google, OpenDNS or sometimes, Satcomm's DNS servers (Karachi - which fall back onto Google's anyway and are pretty fast - except when they're not).