We have tested AVG and AVAST against the same threats and AVG came out tops.
However we could not complete our tests for Kaspersky at that specific stage (about a year ago). Kaspersky has improved since our last test and we are in the process of testing it again. From what we have seen so far, we can certainly say that Kaspersky is a good option to consider when it comes to choosing Anti-virus and Anti-spyware protection for your PC.
Grisoft, the makers of AVG, has show great commitment and great success against the fight against malware, especially if you take into account how effective their free versions are. AVG Free Edition is in several cases much better, more secure and provides better protection than several other well known commercial packages.
The best anti-spyware solution in our books is AVG Anti-Spyware.
You can read our take on these applications on the following pages:
avast! 4.7 Home Edition Review
AVG Anti-virus Free Edition Version 7.5.432 Review
AVG Anti-Spyware 7.5.0.50 Review