I used a nameserver tester to compare my ISP's servers with Google and OpenDNS's. OpenDNS came out on top for me at that time and I was interested in their filtering ability too so I went with that.

IIRC it was https://code.google.com/p/namebench/ that I used for the speed comparison. Just using it now I see it does a comparison with the popular global DNS providers as well as optionally local providers - it also can test for censorship.

There are many DNS benchmarking tools; https://www.grc.com/dns/benchmark.htm looks quite good.