Malwarebytes Free Download vs Paid Subscription

The main difference between the two is the paid version keeps a live function running in the background to watch for things like ransomware. If it detects something other than FileVault encrypting your data, it will attempt to stop the app and disable it.

Malware comes various forms. As Mac Jim ID noted, adware will be in your face, since pushing ads is its entire purpose for existing. Other types of malware will do whatever it can to NOT be detected. Such as a key logger.

You don't need either one. If you are deceived into installing adware you can fix it yourself using the Finder. You don't need to pay anyone and you certainly don't have to install anything else.

Of course it's easier to avoid installing it to begin with: Effective defenses against malware and other threats - Apple Community

Just use the free version only when Malware is suspected. It will be no secret if you have Malware, since the whole purpose is to make itself known. You will see multiple notifications claiming you have a virus or websites will be redirected to sites that will fill your screen with ads. There is no need to have any software constantly monitor your computer.

I think MalwareBytes is a very reputable program and have used it myself, but that does not mean I want to have it running constantly on my computer consuming resources when it is not needed.

I have no problem supporting a developer for a program that I find useful, but if the only option is to have constant monitoring then I will continue to use the free version only when needed.