YCbCr is simply the 3 components of an NTSC signal split, it is what is stored on a DVD and does not usually leave the player, YCbCr is usually carried over a single cable and is digitally encoded. YPbPr is used to carry HDTV and progressive video, it is analog, and are the familiar 3 wires we all know and love.
YCbCr inputs or outputs are usually mislabled YPbPR. However, the terms are used to interchangably, nobody really cares at this point.