Nitpick: they’re complementary. LR has cataloguing/sorting/filtering/metadata handling features that PS doesn’t have, and has an “edit in Photoshop” option for the more complicated workflows you mention. Not many people would enjoy using Bridge and PS to sort their photos.

I am a professional Lightroom user that deals with about 700-1000 shots per week (automotive photography). I estimate that I use the Lightroom–Photoshop–Lightroom round-trip editing for retouch on about 10–20% of my shots. The pair taken together is really powerful stuff and I haven't found anything better for dealing with large volumes of photos, each of which requiring adjustment of some sort.