I've always liked that this plugin combines an xml sitemap with all the other options you need to make your WP site SEO friendly. Clean, easy-to-understand interface, as well.
Plus, you get a single place to enter the Webmaster Tools verification codes. That comes in handy, since Google Webmaster Tools has always made me re-verify sites every few days, to the point where I just stopped bothering with it. This may help me staring tinkering with that stuff again.