Mac is very loosely based on Unix...it recently gained unix certification for the first time, yet it still lacks many options that other unix OSs have. If anything, OS X is the prime example of how to make a bad Unix OS. Hell, its 64-bit support is worse than Vista's.
A Mac is still a personal computer. My computer in my den running Debian is a personal computer. The computer I set up running OS X for when I help friends with OS X problems is a personal computer. My main PC that runs Vista Ult. x64 is a PC. My servers in the basement are servers.
Also, OS X has all of the security issues as FreeBSD, yet it is much harder to fix the insecurities, and even worse it is primarily marketed towards computer illiterate people (then again so are Windows PCs, although with a good router/hardware firewall and a good AV Windows can be quite secure) who don't know how to secure an OS X system. The main problem I have with OS X is that it focuses on security through obscurity, and as such there are no decent AVs. I feel fine when I run my windows PCs in basic user accounts with a good AV like Nod32 or Kapersky, but I never feel at ease when using my OS X rig(s) because there are no good AVs. OS X's popularity is increasing, though, so hopefully a good AV will come out some time (especially since viruses are starting to target it
http://www.boygeniusreport.com/2008...-x-trojan-and-backdoor-tool-are-on-the-loose/ ). Stuff like that just pushes me to Vista and more obscure Unix OSs (I love Debian with x and OpenBSD), because I can more actively protect myself from attacks.
So, in my opinion...OS X is less secure than Vista, if you know what you're doing.
Back on topic, get some ebay triggers and a cheap light stand and read strobist!