There will be more available in Avast Free as as far as I am aware, I believe the difference is in the protection components. Avast incorporated some of the code-base from AVG after they acquired the company into Avast software regarding static and dynamic but I doubt the products are identical in terms of what is available now. I'd imagine they acquired AVG to give "Avast" branded software a boost, and kept the AVG company up and running to generate more income from all the existing AVG customers.
This is speculation though, I can't say for sure.