Malwarebytes work is to hunt down new and constantly changing malwares which poses the biggest threat to the average users, who faces the possible attacks directly from the web. Whereas the work of the antivirus is to protect you from the known and dangerous malware. Malware doesn’t look for that virus which are forgotten or might not have been seen for few years, But it is always said precaution is better than cure and I’ll suggest to keep both on your desktop to keep your desktop prevent from any type of malware error’s.