LR has speed over photoshop IMO. Of course, it's horses for courses, but if you're only doing basic edits like levels, recovery, tweaking exposure etc, it's quicker for me to zoom through them all through one interface, rather than taking them one by one from bridge (even just using the raw interface).
Obviously LR isn't as in depth as PS, no usage of layers, for example, but it's quick and handy for me. It's easy to find things, I can seperate things out how I want them and it generally makes my workflow quicker.
Depends what you're used to I guess