What is the faster way to determine if nsIDOMNSHTMLElement is an anchor

Hi,

Can you please tell me which is a faster way (run time performance) to
determine if nsIDOMNSHTMLElement is an anchor?

nsIDOMNSHTMLElement* element;
 nsCOMPtr<nsIDOMNSHTMLAnchorElement> anchorElement =
do_QueryInterface(element);
 if (anchorElement) {
  // it is an anchor element....
}
or
nsIDOMNSHTMLElement element;
 nsAutoString name;
   childNode->GetNodeName(name);
 if (name.LowerCaseEqualsLiteral("a")) {
 // it is an anchor elemlent....
}

Or there is an even faster way?
Thank you.