Pros and Cons? Well thankfully you can buy oem or retail on microsoft, only retail on mac os, linux though you can get for free. If you are going to add another operating system first see about getting a bigger hard drive if its a 40 gb. Where Sony went right was by using a laptop hard drive so pick your favorite place. Consider taking out your current drive and find out if its a sata or ide type that way you know what to get. The PS3 is exactly like a computer and will recognize a larger hard drive and format it for you, and the mice thing is that the os for sony is not on the hard drive so no fuss, unless you've got game data you want.
Linux pros and cons: Ubuntu is is probably the most user friendly version out, and just like mac and vista if I'm not mistaken its 64 bit. Linux is for the most part based off the original mac OS called UNIX, and because there are not that many mac and Linux users out there, as far as the ratio of home users go, viruses are few. As far as using keyboards and mice go; its usb you don't need any drivers. Only issue is if you want try the latest PC games using Linux, you'll be waiting a few weeks. I'd say Linux might be the safest if not then cheapest way to go.
MAC os pros and cons: Because of user ratio again viruses are few, only issue I can really think of is that the gaming market for mac is very poor. Games like crysis, unreal 3, or when fallout 3 comes out won't happen for 6 more months! Mac is not designed for gaming, however it certainly can handle it! Bear in mind mac software has done the special effects for movies like Matrix all the way through revenge of the sith, and its very good on the audio recording and mixing. Due to this level of thinking many don't use macs because of these niches. On the gear side though if it works for a PC it works on a mac 7.5 times out of 10.
Microsoft pros and cons: The strongest in gaming market, and for equipment usage (i.e. build your own system). Just about nearly everything made will have Microsoft drivers first, followed by mac unless strictly made for a mac. Unlike either OS vista has got to be the biggest system hog ever and it don't matter if its the 32 bit or 64 bit flavor. Of all OS this will guarantee-ably have the most virus out to destroy it, or for trying to take your personal info, and it don't matter if you use xp either, virus stuff applies in spades! Vista also has something called UAC user access control that literally acts like an mcp Master control program, which will ask you for permission for nearly everything. IF you go vista shut it off to avoid this annoyance, tap f1 and type in UAC the rest should a no brainer. Sooner or later xp will be completely phased out which means you'll be having to go vista. Its not bad at all, and is about as stable as xp became when service pack 2 came out. If your familiar with xp then it will of some relief that not much has changed. What did is that there are more options for placing downloads and other various files.
Bottom line: You will need virus protection no matter what operating system you use. My pick would be Linux, followed by mac, and lastly Microsoft... the last thing I'd want to hear is how vista fried someone's PS3.
