No, OS X is --NOT-- more stable, secure and less resource hungry than Vista, especially not when we are comparing OS X Leopard in 64-Bit mode with 64-Bit Vista. In my experience, 64-Bit Vista outperforms Leopard on the same computer. And it is also less error prone than Leopard.
Macs also no longer have the better resell value that they used to have in the PowerPC days. Macs have become a mass market commodity, and accordingly their resell value has significantly declined; it's still better than that of an average PC, but it's no longer as good as it used to be.
Vista Virus
http://www.infoworld.com/article/05/08/04/HNvistaviruses_1.html
http://www.pcpro.co.uk/news/news/103850
Where is the OSX virus??? No, trojans don't count as it requires the user to authorize the installation.