AV Repair function

If you mean the ability to remove a virus from a file that was previously virus free as opposed to simply deleting a virus, (healing) that function is very rarely needed these days. Nearly all of the time a virus is found it can't be healed because it is the virus or a part of it. Only option is to delete/quarantine it. Healing goes back to a previous generation of viruses that add data to already existing files on a computer. They were pretty much simply destructive viruses as opposed to nearly all today which have a function (or more, eg- data mining/spying/etc) to perform and there's no reason for them to infect already existing files.

The exception would be altering certain Windows boot files to start the virus at boot time and in this case I don't think there's any difference in abilities between freeware and paid-for a/v's to deal with the issue if it should occur. It's really an issue of the quality of the a/v as opposed to its price (or lack of)