No AV software should be used on a Mac. There are no Mac viruses. Period. They haven't existed since the release of OS X, 10.0.
Viruses are malware that self-propagate. While a couple were developed (over 10 years ago) by security labs that worked, the method by which they worked were reported to Apple and patched against. There has never by a virus in the wild.
Worms are also essentially non-existent. The only known worm was Oompa-Loompa. Also known as Leap-A. That was also patched against at least 10 years ago.
The main threat are Trojans, which is any malware the user must be tricked into installing, whether you knew you were doing it or not. They can't get on your Mac by themselves. All of these are Trojans since they all require action on your part to get on your Mac:
Adware
Back doors
Ransomware
Key loggers
Spyware
And anything else in a similar vein.
You may think AV software would be helpful for these. They aren't. The AV software can't know what it is you're installing and/or running until after the fact. Few will even alert you to the malware you just installed. So, they're useless two ways. They can't stop you from installing or running a Trojan, and almost never even let you know you did.
Your best defense is to use your head. Don't download anything from P2P, file sharing or pirate sites. Get your software only from legal, legitimate sources.