The only real difference that we can notice is a missing Ethernet port, which isn't a big deal for most. There's no mention of the copper heatpipe in the unique features sections for the GA-X38-DS5. The boards even seem to come with the same accessories, so we can't quite figure this one out, as this can't save Gigabyte a lot of money and this is usually why there's a cut-down version of a better board.

Either which way, this is what the board will look like and if you're happy with a single LAN connector and want to save some cash, then this might be the X38 board of your choice. You can find the product page here
On a side note, Asus has updated its X38 product page again and the Maximus Formula has appeared. You can find the board specifications here