Prior to 2007, I was a PC guy, working with Windows XP and beta-testing Vista before I started to get frust over the slowness of the Windows (both) while compiling my LaTeX codes for my postgraduate studies. That's when I started to switch to Linux, trying most of the famous distros out there, i.e. Ubuntu, Mint, Fedora, gOS, PCLinuxOS etc.
And hence, I turned into a Linux guy. And honestly, I found that Linux is better than Windows in many ways, except for playing games. The system seldom hangs, there's Compiz-Fusion (now that's what I call Wow!!!), the fonts look nicer onscreen and most importantly, whenever I format the HD and reinstall the system, I don't have to spend like half a day to find and install all the drivers of the hardware that I have.
After 2 years of playing with Linux, I finally took the plunge and got myself a MacBook late last year. So I've been a Mac guy since (man... imagine the identity crisis that I, a geek had to go through :-p). So how does Mac compared to Linux? Well, in terms of stability and security, both are free most malicious stuff out there at the moment, so both are equal on this part. But for practicality and ease of use, Mac has a slight upperhand over Linux. For instance, getting Chinese input support in Linux is still not that easy to setup. And for newbies, working with the Terminal in Linux is quite cumbersome and is not something that most people would like doing. But overall, I still think that both are better than Windows, unless if you are talking bout playing games.
So here's my ranking list for the 3 OS'es (just my personal opinion, no pun intended :-) ):
1) Mac (Leopard)
a) gOS Space (the last that I used before switching to Mac)
b) gOS 3.0 Gadgets
c) PCLinuxOS 2007
e) and the rest of the distros that I've tried in no specific order
b) 7 beta (better than Vista but still hanging)
c) 98 (the King before XP)
d) 95 Plus! (could still remember the hype back then)
f) Vista and Me (equally bad and frustrating to use to me)