Is a mac faster than a windows cp?

i was gonna buy a cheap acer with windows 7 starter its 1.66ghz but i heard windows has all kinds of stuff running n background and is more open to virus my friend who uses mac says he never had a virus and his seems to do stuff ALOT faster like convert videos.....acer has 1.66 ghz proc intel 4 core and 2 gig ddr the mac has 2ghz intel core 2 duo proc and 2 bg 667 mhz ddr2 sdram but mac seems alot faster at everything is the mac really a better buy for speed and virus?