Depends on purpose. For gaming and GPU intensive tasks, Windows is definitely superior. This is because much better GPU driver quality. However, for any other tasks - Linux might be is generally is superior. I use it on my desktop station for years and my productivity is higher than on Windows. Linux stations are also easily maintainable because of SW packaging and maintaining via package managers. I could write many pros/cons of both OSes, but it would be much of a text for a single post.
with Linux, is antivirus necessary? I have no experience with Linux, and was wondering if viruses for it exist.
Linux can have security flaws. If you use an actively supported distro, those flaws will be patched. Linux can be infected, but it's not as prevalent as with Windows. There are anti-virus programs for Linux, but not frequently used by most Linux users. One anti-virus scanner program for Linux is ClamTk.