Depends on what you want to build. iOS software and you will need a mac. Microsoft stack and you will need windows. If you are doing more general web developme

Depends on what you want to build. iOS software and you will need a mac. Microsoft stack and you will need windows. If you are doing more general web development then there is a good chance you will be using a Linux server so it makes sense to learn it - your dev environment will be more similar to your production environment. There is plenty of open source software and material available so you can try things out.