Deployment descriptor

Encontrei esssas 2 formas de iniciar o arquivo web.xml:

a)

<?xml version=“1.0” encoding=“ISO-8859-1”?>
<!DOCTYPE web-app
PUBLIC “-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN”
“http://java.sun.com/dtd/web-app_2_3.dtd”>
<web-app>
</web-app>

b)

<?xml version=“1.0” encoding=“ISO-8859-1” ?>

• <web-app xmlns=“http://java.sun.com/xml/ns/j2ee” version=“2.4”>
  <display-name>Aplicacao web simples</display-name>
  </web-app>

Qual devo usar? Qual a diferenca? Isso depende do container/servidor usado?

Muito obrigado.