It appears that using a nameserver with a host name on the same TLD as your own is fastest, this may seem like hocus pocus, but computers are a strict discipline and therefore i need to explain, i can’t give you statistical evidence, this is not biology.
So, why is it so ?
Assuming your website is example.com you are advised to use nameservers such as ns1.host.com, if your domain name is example.cc, you are advised to use a nameserver such as ns1.host.cc , surely this is not an option to those of you using shared hosting, but i am talking about those who run there own nameservers for one high traffic website.
Unless you have the namserver host with the same TLD, Verisign in the case of most generic TLDs (And the .CC) will not pass the GLUE records with the namserver host address, this will result in a few milliseconds lost in fetching the A record of the namservers.
The reason behind this is probably that every TLD has it’s own database, and queries to that database do not cross over and get data from a different database, it passes the task of checking the A record to your recursive resolver. Or maybe it does not want to answer authoritatively for a different TLD hostname to not cause confusion
So, having your domain and the namserver on the same TLD makes a slight difference with every query, surely, $7.5/Year to save all the extra requests coming your way, and saving every visitor a few milliseconds (Or a few hundred milliseconds in some cases) is not such a bad idea, Or tell you what, why would you need to buy more domains, just register your nameservers on your own domain, so example.com uses ns1.example.com and ns2.example.com and you are done.
Happy DNSing
Query safely
I have included the explination of what Glue record are here