First, people don't usually 'Choose' Windows. It is what every computer Dell sells, it is what you get if you don't buy an Apple computer. Does Lenovo offer OS X? So it is not a 'choice'. It is ironic that you have to buy an Apple computer to have a choice, between Windows or OS X.
Actually this is incorrect, you CAN order Dell PCs with Linux, or no OS at all. What you CANNOT do is order a Mac legitimately with Windows on it.
Windows is less secure because the user base is less educated, less knowledgeable...
I have heard this before from the occasional Mac user, yet I find it perplexing because you'll never see an article like the one below this that explains how to buy a Windows-based product. Apparently it's gotten so bad now that Apple users need step-by-step directions from Apple in order to survive.
On a serious and factual note, the notion that Apple consumers are more educated was objectively disspelled a couple years ago. They actually found that the iPhone was most popular among middle school and early high school kids, and 34-50 year old stay at home mothers. Android, and surprisingly, Blackberry dominated the professional sector.