As I see it, Lightroom is what you use when you have several hundred raw files on a card. It does great with converting, cataloging, and thinning out the ones you really want to keep.
Photoshop is the program that manipulates a single photo to wring out everything from that one image.
Lightroom is for the bulk, photoshop is for the specific photo. If you don't do alot of heavy manipulation (me) Lightroom is the main answer.