The DX50 is probably going to be more expensive. Wait a month or two and see how these are priced. So far dealers are taking preorders for the X3 at $199, which is full list price. I have a feeling early next year the X3 might be discounted to $150 or less. Lets see how much the DX50 is discounted to in a few months. It does seem like these will probably be quite a bit cheaper 6 months after the first release than their initial prices.
I am not thrilled with either, and want longer battery life. I am hoping Sandisk will release a new player at the end of August.
I highly doubt that this will happen.