Big problems lead to flashy headlines. On the other hand, the estimates for the number of viable Macintosh viruses range from 20 to 50, and many of those won't work under Mac OS 8. So, by this simple estimate, the problem appears a hundred times worse under Windows. Of course, this feeling of superiority you get by knowing your Mac has far less chance of being trashed by a virus would fade quickly, if it did get trashed. The truth is that most viruses are fairly benign and won't trash your system.
Problems generally appear because of unintended side-effects.
Truly malicious viruses are rare because, if they trash the system they infect, it's harder for them to spread. There are easy and effective measures to avoid both benign and malicious viruses. A number of programs are available to prevent virus attacks. For years, I've been relying on a free program called Disinfectant. I like Disinfectant because it's simple, fast and completely unobtrusive.