I would switch to linux, probably for the sake of learning something new :-)
(also opens the possibility of apply that knowledge in any unix server... well, some at least)
From a web developer point of view, it (almost) doesn't matter if you know windows or unix. Mostly you'll develop/unit
test in windows environment and deploy for QA and production in unix/linux... knowing how to navigate/solve problems in each environment comes very handy.
BTW, maybe is true, they are too many web developer, maybe not. Maybe you'll be a better one, maybe not, but don't let the market decide what you like.
Do what you really enjoy and probably you'll be very good at it...