If you make a malware for Windows, you will have a larger target area, and hence, more chances of being successful.
One of the major reason behind PCs getting more malware attacks than Macs has simply to do with maths. Although Macs are generally considered a more secure platform than Windows, they are also susceptible to malware attacks. Before we get into the review, let us first bust a myth which says that Macs never get infected with malicious software (malware).