What is the difference between instanceof and Class.isAssignableFrom(…)?

Which of the following is better?

a instanceof B

or

B.class.isAssignableFrom(a.getClass())

The only difference that I know of is, when ‘a’ is null, the first returns false, while the second throws an exception. Other than that, do they always give the same result?

When using instanceof, you need to know the class of B at compile time. When using isAssignableFrom() it can be dynamic and change during runtime.