Lightroom is a workflow app dedicated to working with and storing raw image files (primarily). Photoshop is a pixel editor...ideally, you need/get both. The dividing line is, do you do a lot of stuff in Photoshop? Retouching, image compositing, image manipulation? Photoshop. Shoot a lot of raw and generally need to only tweak white balance and tone/color, Lightroom. Not sure? Get both and figure out what is best after you get it...Adobe has a 30 day return policy.
