Windows Servers have an incredibly good GUI that Linux lacks a bit. Even though Windows Server has a CLI, its not as user friendly as that of Linux. So if you are a fan of old DOS, you will find working with Linux commands comfortable than with the commands used in Windows servers.
I have started using Linux some time around 1993 or 1994 when I still had to compile the kernel for my computer (pre-version 1.0).
What I really like about Linux is the ecosystem that has sprung from it, including things like git (which is now my default version control system), which was developed by Linus in order to do the version control for the Linux kernel.
Workwise, I like using Linux because many of the free and open-source tools for bioinformatics are easily(?!) configured and compiled for this system.
Best thing about Linux is the freedom it provides. You want a video editing tool, you just grab it from the repositories. Want an image editing app? You got it from the same place. Same for office suites. No need to go an purchase this and that piece of software. You can argue that the quality of the free software is not good enough. But that's quickly becoming more a myth than a reality. There are other reasons why professionals are using proprietary software. However, as I said, this is quickly changing.
Did you know that the visual effects in "The Man in the High Castle" series are entirely made with the (free software) Blender suite?
My favorite thing about Linux is that its free and kernel is open to development. Unlike Windows or the proprietary operating systems Linux offers an open source OS. This is important as if a major security flaw is detected, there is a better chance for correcting the flaw, than wait for others to correct. Though, Linux is not that user-friendly it is surely customizable. Customization is big thing in operating systems and when the user is not a "geeky" user.
Not having to install Shell.
Any other answers are wrong.
If you are a long time windows user, you would also probably agree that the fast startup times are a great part as well.
I love the variety of Linux flavors that are out there. Do you want bleeding edge? Try Archlinux. Are you wanting a more stable version? You have Debian to try. Do you want a user friendly desktop environment? You have Gnome, KDE, Cinnamon, XFCE and more to choose from. Are you a power user that loves to get their hands dirty with the build? Try Gentoo.
In addition to the various linux distributions, the software repositories are really good. Whether you like pacman, apt-get or some other package manager, the selection has really improved in quality and quantity. Almost all of it being free.
Another huge plus, in my opinion, for any Linux operating system is that it tends to be more secure than Windows systems. There are far fewer viruses that affect Linux. Since most Linux users have a User account and a separate root account, the core system remains untouchable for most viruses.
Kubuntu. While Kubuntu is a Linux distribution, it is a technology somewhere in between Windows and Ubuntu.