I suggest that you google "benefits of openDNS" or similar to see what benefits may be obtained. There are several, including enhanced "family" filtering, additional protection from malicious websites, digital signing of DNS entries for security etc.
Of course not all will be pertinent to you, but there are many more reasons beyond mere speed.
BUT if you have a laptop which moves between networks then your ISP's server may not be accessible from another network - hence the value of using a public DNS server like Google.
In that scenario you are likely to be using DHCP rather than static IP configuration, in which case the DNS server details should be passed by the DHCP options in the scope.
SD