The sales guy at my Best Buy says they sell about the same number of PS4 and XB1, give or take a couple, but they sell all the PS4 on Sunday when they come in, and the XB1 just sells steady all week with no supply issues. If people had to show up at a certain time or place to get the XB1 they probably would, but there's no real reason to.
But if they sell the same amount, what difference does it make at this point in the gen? I really don't think anyone is walking into a store wanting an Xbox and then saying "Oh there's too many of them on the shelf. I better not buy it."