Well from my point of view gaming, familiarity, price, range of hardware, ease of setting up a dual boot system, range of third party software available and upgradeability. I've never had a problem with a virus and since installing a good firewall I've had no sign of spyware. I've rarely had to 'fight' with windows and when I do its usually to do something not entirely legitimate and on the very rare occasions when it crashes its usually my fault.