Hey Ejr,
Malware, Spyware and Adware come in different forms/functions. Hence the need for a Smart Update feature. As new infections are always being created everyday, new signatures are always needed to detect and remove these new infections.
There are also some viruses that shut down your computer and are not neccessarily malware. I am currently using the 30 day trial version of PC Tools AntiVirus and it seems like a very good program.
We'll see how that goes.