(LEO) The kind of orbit used by communications satellites that will offer high bandwidth for video on demand, television, and Internet communications. A satellite in LEO, in contrast to one in a geostationary orbit, is not in a fixed position relative to the Earth's surface so several satellites are required to provide continuous service.
[Ovum report, "Applications for the superhighway", John Moroney].
The Delta IV can carry a larger payload into low earth orbit than the Atlas V, 60,779 lbs.
There is, of course, cheapness to be considered -- the dollar per kilogram bill for putting a payload into low earth orbit.