I'd argue there is really no such thing as a low maintenance developer system. Any good developer will need to customize their environment alot to be as productive as possible, and this means different things for different developers. Personally I choose linux because I like the development tools available there best and find it easiest to make any changes I need. That said though, OSX and Windows are perfectly legitimate choices for different people. From what I've seen though, OSX is no more low maintenance for your average developer's "requirements" than anything else.
For web development though I'd say osx or linux. I just havent seen sort of tools on windows to justify putting up with it unless you're focused on microsoft technologies (or a hopelessly entrenched windows user).
