I've had the opportunity to test out the Kindle 3 Keyboard for a month, and now i have the new Kindle 4 non touch. I just bought it a few days ago. But now i'm thinking, are there better devices? I'm still new to eReading, but i've heard ePub is a better format then Mobi in terms of it's capabilities. My question is, having tried Mobi (AZW) , would switching to ePub be a better investment in the long run? If so which devices are good for ePub? Are there any devices that can play ePub and Mobi without DRM? Should i return the Kindle now and get something else?
Thank you for any help

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Edit: Also, best stores to buy ePubs?