While there are tools, usually the same tools, for both OS's... I personally have found that anyone who is serious about hacking should have a working knowledge of both OS's. Usually when I do any serious hacking, I use BackTrack. This is a Linux OS that has all the tools and tutorials that I need to crack a system. The problem I find with Mac OS X... The hacking tools are readily available on the internet if you know what you are looking for, and where to find them. So to put it simply, it takes more time to research how to hack if you are using a Mac.
I just want people to know, I love my Mac. I upgraded to Lion the day it came out. I love my Ipod touch 4G, and my Ipad. However I also love my Linux desktop. I can hack just about anything with it.