DNS is much faster. whois is usually rate limited and a lot of whois services have restrictions on automated querying. Obviously, whois is more accurate though.

DNS is much faster. whois is usually rate limited and a lot of whois services have restrictions on automated querying. Obviously, whois is more accurate though. So. When I need to test if a bunch of domain names exist, I first of all do a DNS NS lookup. If you get a result, you know the domain exists. If you don't get a result, then do a whois.