Linux is far more effective than Windows on servers. Systems like Windows are 90% user interface and 10% OS.
I recently installed the latest Ubuntu server on a 15-year-old computer that originally came with Win 2K. It runs perfectly, with very low CPU and memory usage at idle.
Have you ever installed server core or nano server?
I was working in the IT department of a rather large company based in San Jose area. Or printing solution was running 4 Linux / CUPS based print servers for all of our print queues. At the time, there were 13 main campus buildings, each composed of a couple of floors. So I estimate 10,000 employees on any given day.
Microsoft came in and said they could do better. Being good corporate partners, we decided that Microsoft should be given the opportunity to replace the Linux boxes. After installing 20 brand new MS servers, and still not able to handle the load, MS was asked to leave.
That was during the NT era, so things may have changed by now.