For me one of the biggest differences is the ability to do things in bulk. I can have a whole set of photos that need some basic editing such as changing the color balance and bumping up the blacks. I can do them all at once in LR. There may be a way to do it in bulk in PS, but not that I've found (granted I'm a PS novice). I also find the crop functionality of LR to be quicker and easier. I own them both and do about 95-98% of my work in Lightroom.
Batch actions in PS would handle all of that quite nicely.
True, but you'd need several hundred batch actions to cover the possibilities that lightroom lets you do in seconds. With lightroom, You just check those attributes you want copied, and select just the images you want them applied to. You do not have to do a whole folder. The flexability is what sets it apart.
You can do this with PS/ ACR too!
While in Bridge highlight one photo you have edited and press shortcut [option+command+C], then highlight any number of photos shot in the same lighting conditions and hit [option+command+V] and ALL of the settings will be applied to the photos. A dialogue box will even pop up with options to select which changes you want to apply.
Note: This is obviously only for ACR edits.