The brand of camera should not dictate the software used for post processing. If that was the case, the the answer would involve the disc included with your camera.
With that said, I work exclusively on a mac after having moved from a PC based editing system. I first started using ACDsee for post processing from my camera at first, a Minolta Dimage A1, then a Canon 30D. I then moved to the software included with the 30D and finally purchased Lightroom 1.x for PC and have never looked back. When I moved to Mac and upgraded to Lightroom 2.0.
Both Lightroom and Aperture have a 30 day trial. Try them both, and decide for yourself which software better suits you.
Admittedly, I have never used Aperture, but have sat in on a number of Apple Aperture presentations. There are some great features, however, one thing I have never come to appreciate is the method of categorizing shoots as "events" rather than the date I shot on.
So, download and install both trials shot a lot, spend a lot of time in both programs.