I provide a service to customers that uses DDNS to authenticate the customer. If my customer's public IP changes i want my service to know about the change as soon as possible to make sure they stay authenticated.

Would it make sense for my service to use Dynu DNS servers (e.g. NS1.DYNU.COM->199.233.237.18
NS2.DYNU.COM->176.56.236.89) so any changes of my customers IP would be updated faster. Or would using 8.8.8.8 be just as quick?

I use you Dynu for DDNS.

Thanks

Using Dynu DNS servers will be faster if you are querying the IP address changes for hostnames that use Dynu's dynamic DNS service. The IP change happens first in Dynu's name servers then propagated to public name servers such as Google 8.8.8.8. There won't be too much a difference though if you have a low TTL.

However, Dynu name servers are not public name servers so they only respond to DNS queries for domain names that are on their name servers.