Should I use string.isEmpty() or "".equals(string)?

I'm usually testing this alongside a string == null, so I'm not really concerned about a null-safe test. Which should I use?

String s = /* whatever */;
...
if (s == null || "".equals(s))
{
    // handle some edge case here
}

or

if (s == null || s.isEmpty())
{
    // handle some edge case here
}

On that note - does isEmpty() even do anything other than return this.equals(""); or return this.length() == 0;?