Windows is more vulnerable because of it's core architecture - there is no separation between the core operating files and the user accessible portions of the system.
IE - you can edit the windows / system / program files / etc folders from your user account - this is why it is vulnerable to viruses because as a user you an inadvertently run a file that will damage your system
IE - you can edit the windows / system / program files / etc folders from your user account - this is why it is vulnerable to viruses because as a user you an inadvertently run a file that will damage your system
With Linux and mac this is not possible.