It all depends on what you do with your computer. If you do a lot of downloading and surfing I would suggest at least an anti-virus and spyware program.

The big different between a suite and just an anti-virus is the extras that come with the suite. You usually have a firewall, spyware program and a restore function within it. If you don't need all these bells and whistles, stick with just a straight anti-virus. A suite will most likely slow down your PC.