I think this depends on what you are looking for. Photoshop is a Photo Editing program, Lightroom (like a darkroom) is a Photo Developing program--mostly. If you're looking for something to change your images into something entirely different from what it really looked like, Photoshop is a good tool for that. If you want to optimize the images i.e. bring up darks, lower flares, basic changes, Lightroom is the way to go. I usually optimize my images, and like Lightroom so I'll say why.
I used Photoshop for quite some time, but prefer Lightroom by leaps and bounds. First and foremost, Lightroom has different functions: Library, Develop, Slideshow, Print, and Web. They are all useful, but Library, Develop, and Web are my favorite. As opposed to Photoshop, you upload your images into a library one time. No more selecting open and choosing however many you want to edit, clicking ok, and walking away from the computer because it took forever. From there, you can select the ones you like of all the images shot and easily view them in Develop mode.
The tools when shooting in RAW are much more precise in Lightroom. The layout is self explanitory, and the menu is put right there in front of you, so you can just push buttons and adjust needles and the picture changes right in front of you. Photoshop requires you to open a window and do this.
I guess I should also say that I am usually working with at least 300 images uploaded at once, and they are usually of events. How long it takes is very important.