Which anti-virus is better? McAfee orr Kaspersky?

I just bought a computer off my friend and it came with Kaspersky 2010 on it. On my old computer I had McAfee Antivirus Plus 2010 on it. Which one do you think is better? I've never used the Kasperskyone before and I still have one download of the McAfee left so I'm tempted to just change it.. I just want the better one. Thanks fo your help :)