We've already said that at its maximum, the GLE can haul more stuff. But it'll also be a smidge more comfortable for passengers, too. The high-rider's wheelbase is 2.2 inches longer than our E450 tester, and that allows for a big 4.8 inches of additional legroom in the second row.
The E-Class still has a respectable 36.1 inches of leg space, but that sort of a difference is very difficult to ignore, especially if you're regularly toting about gangly teenagers or tall adults on a regular basis. That said, the E-Class does have more headroom overall, but the roughly 1.5-inch differences isn't enough to make up for the disparity in legroom.