JanP,
Scot specifically mentioned that the version he based his decision on was the Pro version. 
Right.
On the other hand, Matousec mentions free version in hist test.
The main difference between the two is comfort in using (free does not update automatically, has less possibilities for setting rules etc.), the level of protection is the same.
As you for sure remember, I said that user's feeling is very important at product selection and thus level of comfort can mean a lot. I myself prefer security - that's what the firewall function is, after all - and so I have selected OA. After testing and using many others (Kerio, Outpost, Comodo, even Jetico for a while).
BTW, is there a difference in security level between paid and free Avast? I hope not...