Safer, more flexible, most software is free (and open source), and YOU are in control, not the vendor of the operating system!
It's a more secure than any other OS. Plus it's faster too :)
the options and flexibility not to mention the huge communities/groups you run into on a daily basis
I work on both Windows server and Ubuntu server. First of all, both of them are secure and reliable. I ran a website with more than 15 million pageview per month on a single Windows server using IIS 7 and PHP via FastCGI. It is fast and stable. No downtime.
Linux just gives me the tools I need to develop software. It's also fast, stable and secure,
I think its a fairly broad question since there are some benefits to windows over linux from a development perspective. However I personally have used debian based linux distro's for the past few years I would say to anyone to choose the right tool for the right job.
However some of the benefits of linux may be :