I'm far from a security expert, but this article (or a related one) was posted recently on HN and it covers some fairly technical reasons why Linux isn't as secure as commonly believe [0]. While that may be true, I think in practical terms you are less likely to encounter malware etc on Linux than Windows, but that could very well be because it is a smaller target as you mention.

https://madaidans-insecurities.github.io/linux.html