I always go ebay. If you've a long running account you very often get reduced fees etc. But even though there's 10% selling fee plus the 2 or 3% that PayPal takes, you still usually end up with more than you would get trading it in at a store. I'd say sell it soon though as when the One X launches it will ged flooded. Also, if you plan on selling any games or accessories other than came in the box, sell them seperately as you'll generally get a little more, although its a bit more hassle sending multiple packages.