the biggest myth in the world today is that Macs are immune to viruses..in reality Mac OS comprises of less than 5-10% of all OS available on the market and so virus developers and hackers target computers for more effect, but all said Mac was much more user friendly till Windows 7 which I like better..and u have to take in costs as well...My current Dell Inspiron Laptop(win 7) cost me about 400-500 dollars with a replacement warranty on it for 3 years. A mac will cost you 1200+ and while it is a great device with great customer service and longevity, it is still too expensive. An iphone which is the only practical apple device i have needed or bought(i might switch to a droid when my contract ends) though i do have 3rd generation 120 GB ipod which was a gift.
Since you mentioned viruses, if you do get a windows based device get an anti-virus preferably a macafee while expensive is very much reliable