If that is true I would look at the complexity of the applications being served: Windows servers tend to be glorified desktops acting as a fileserver or maybe just a webserver. Hell out of the 50 some odd production Windows boxes we run about 10-20% of them Are domain controllers!! What a waste!
We have probably 6:50 Windows and 2:25 Unix with two who float between the both as needed. If we had to pick a box to lose and never returned I could guarantee you I could list 30 Windows boxes before I got to one Unix box..
Incorrect. Typical shops I've worked in run the gamut from simple web and file/print servers to active/active clusters. The same roles as the *nix servers.
Uptime leans the *nix way, except for Linux which runs about the same as Windows. Why? Because business units buy Windows and Linux because they're cheap and don't need high availability. They can be built to keep the app up forever but don't want the expense.
Any study that doesn't take that into account is crap.
20 percent of your Windows servers are DC's? What numskull set that up? We get by with 1 percent or less, and those boxes serve DNS as well.