They all have their faults
I've used 'em all, currently using Fortinet (firewall and AV) and like it more than any of the others, but it is not free.
ALL anti-virus software FAILS to catch common viruses SOME of the time (check the penetration tests). So changing from one AV to another it would not be surprising to find something here or there that another has missed.
As for the pl0nker who thinks he is safe on a Mac, grow-up and read-up some more. Perhaps the history of the internet worm might be a good idea for starters. Then perhaps read about the competition to hack into a mac...which lasted...hmmm - no longer than any other system.