There is no incentive for the free commmunity to provide rapid updates to cover new viruses (which appear more frequently than you may think !). The commercial guys have every incentive, if they are slow, people go to a competitor.
You have a valid point, but what about those companies that have both a paid-for and free version? If they have to provide fast updates / definitions for the paid-for versions, they obviously have them available for the free version too.
As far as I can tell, the differences between free and paid-for versions tend to be features and capabilities, rather than core performance and updating.
I am willing to be corrected, of course!
SD