People sometimes ask us if they should submit sitemaps or RSS/Atom feeds -- here's a blog post that covers the different aspects, and the important fields to specify. In short: why not use both? 

If you're also using RSS/Atom feeds, make sure to take advantage of Pubsubhubbub (even if you have trouble typing or pronouncing it :)) while you're at it. There's an overview at https://code.google.com/p/pubsubhubbub/ if you're curious. 
Best practices for XML sitemaps & RSS/Atom feeds
Best practices for XML sitemaps & RSS/Atom feeds
googlewebmastercentral.blogspot.ch
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