I don't have any hard numbers to back this up, but based on personal experience almost exclusively all of the best engineers I have worked with prefer to work with open source technologies and would not touch .NET. One can think of several reasons for this correlation that make intuitive sense.
If pressed for work I'd even work sooner in a Node.JS shop, even if I feel that Node.js is attracting the sort of developers the Ruby community tries to break away from (i.e. the PHP and Java guys)
I'm sure there are good .NET engineers out there, but hiring/finding them is more like finding a needle in the haystack.