They are 99.999% the same.
On the main page of (DOT COM) the DirecTV logo is at the top and the sub-list down the side has DirecTV at the top, but Dish is just a bit lower down, and all the pages are blue.
On the (DOT TV) it is the exact opposite but all the pages are red.
I have seen no other differences. It is very odd for an e-tailer to do that, because it might make you think you browsed to the wrong site if you are used to the other.