I guess it depends in what you need.
Aforementioned, Norton's SONAR is very powerful, but very sensitive. With higher false positives, it offers higher protection rates. Any suspicious activity usually triggers it. As well, Norton Insight is very helpful in matters of helping you identify the origin and safety of a file.
Unlike SONAR, Kaspersky Security Network IS NOT a behaviour blocker. KSN is a cloud service which uses data and information retrieved from its users to build a complex threat database. The proper module to compare SONAR with is System Watcher. Both look after suspicious activity within files to classify them as either malicious or safe. This module is very efficient and smart, a bit more precise than Norton's, therefore with fewer false positives, which of course may lead to one or two misses. Anyways, Kaspersky's System Watcher ain't the strong point about the product, but the addition of it with KSN and Application Control.
Finally, Avast's CyberCapture is decent enough, but it's not as smart as it should be, considering their huge database. Avast's biggest strength are their signatures due to the amount of users they possess, and the amount of data they can gather. I'd say Avast's strong point is Hardened Mode and Sandbox (paid only).
I hope this helps.