Here are my Reasons for choosing google public dns:-
- Over last months, my ISP has had DNS outages, but Google has not.
- Google's 220.127.116.11 is anycast, so it gets you a nearby DNS server automatically.
- The ISP DNS server should be closer, so less latency. Then again, Googles DNS is likely to have more in-cache, so possibly faster to answer. Another good thing is that Google's DNS servers validate DNSSEC, most ISP DNS servers do not.
On a side note:I wouldn't suggest using OpenDns, it specifically breaks geolocation and load balancing for a number of services, most importantly things hosted on CDNs. Using OpenDNS can cause you to get suck on an overloaded cluster and performance goes to shit.
Their service is really designed to block the sites your kids should not go to, or they might grow up too fast. And they do track their free users, cause they test with them (or so I've heard).
Follow the instructions here to set up Google Public DNS.