Noise control is better in Lightroom for most images. If that is your main concern and would cause you to turn to plugins or third party programs for every image, then you may be better off with Lightroom. I think that modern camera sensors are so good that you don't really need to obsess about noise. I rarely use it for anything below ISO 800, and maybe not even for 1600 if the shot was during daylight hours.
Lightroom also has the awesome targeted adjustment tool and the ability to rotate an image instead of just straighten it. Even so, I still prefer Aperture because of these things:
- Clone brush & Heal tool
- RGB levels & curves
- Highlights & Shadows
- Add multiple instances of levels, curves, colors, etc (similar to layers)
- Brush effects in or out (similar to masking)
- CMD+Click to view multiple projects/folders/albums in same window
- Option+Click to open multiple projects/folders/albums in tabs
- Able to switch between metadata & adjustment panels while keeping same view of current image or thumbnails.
I used Lightroom on Windows and when I first switched to Mac. I'd have no problem going back to it if needed. Both are excellent programs.