I will tell you what. You set up a server running Windows and I will set one up running Linux as we will use exactly the same
motherboard, processor, memory, and hard drive.
We will see what runs faster and cleaner. Yes Windows has made improvements but it is still a resource hog. I have played with computers for 26 years and have seen many things.
Microsoft's advantage is that anyone can point and click and make it go. Linux requires far more skill and ability with a computer and this is the reason that Microsoft is "gaining" on the server front. Most people are just to darn lazy to actually open a book and learn something, they want results instantly with no experience or know how.
I would never expect to sway someone away from Microsoft. I have used both Linux and Windows servers. I have also turned down hosting of dedicated machines for large sites as they specified Windows ONLY regardless of their software can run on either.