Well,i believe both programs are pretty good...Both have good detection ,when we talk about signatures...F-secure has great behaviour blocker with Deep Guard,but it does produce many false positives...Avast has more feutures than F-secure...Avast from my point of view has better cleaning capabilities as well,when it comes to removing malware...I 've had issues with F-secure failing to clean the malware that was detected by the scan engines...F-secure is lighter when it comes to impact on the system...F-secure is very easy to use ,the interface is quite simplefied...But Avast has more options and if they are tweaked in the right way,you can rely on it for good protection...I can only say this...The choice is yours...