I don't know witch antivirus is better can you tell me?

ok a while ago my computer got infected so i took it to a computer store so they could clean it out and they did but when i turned it on they installed a virus protection called symantec endpoint protection but i have a different virus protection called norton antivirus 2009 with antispyware it cost me 34.99 so now i don't know if i should install the one that i have or keep the one that it already has so can you please tell me because i don't really know i just buy the one that sounds good and that a lot of people have.