Windows VS MAC in virus Testing

This is a forum to ask the opinions about the virus suseptibility or each OS to deturmin what would be best for a corp enviorment.

I always thought that very few if any virusus are written for Macs because of the filing system they use in the sense that with Windows if you infect 1 part then the virus can easily spread throught the machine where with Macs the way in which the file system is designed if one part gets infected its impossible to spread throughout having said that im certainly no expert and im sure someonelse on here will have a more definate answer.

"While the Macintosh is generally considered to be more secure than the Windows PC, many security researchers believe that this reputation is not attributable to any superior security practices on the part of Apple. They say attackers have been deterred by the Mac OS X's more secure Unix kernel and the product's less widespread adoption." -- www.infoworld.com/article/06/12/19/HNapplebugs_1.html

However, this other article claims that OpenBSD is the most secure OS -- www.infoworld.com/article/06/12/29/01OPsecadvise_1.html

what about the more bussness setting? Networking?