The "Typhoid Mary" Scenario
Macs are excellent carriers of Windows malware. You won't get infected, but you can pass a malicious .exe or macro-laden Word doc to a PC user. ClamAV excels at detecting these cross-platform signatures.
The "Second Opinion"
If you download a suspicious binary, ClamAV allows you to run a manual check (clamscan) against a different database than Apple's.
Cost Efficiency
It is free, open-source, and does not harvest your browsing data (unlike many "free" commercial AVs).
Do not install ClamAV if,
You are a casual user expecting a "set it and forget it" shield that sits in the menu bar.
You want protection against phishing URLs or web-based attacks (ClamAV does not do this).
Install ClamAV if,
You frequently share files with Windows/Linux users (email attachments, USB drives).
You run a home server/NAS on the Mac mini and want to automate scanning of incoming directories.
You are technically proficient and comfortable using the Terminal.
Use Case Score
Personal Protection: Low (Apple Native Security is superior).
Network Hygiene (Protecting others): High (Detects Windows/Linux malware).
Resource Impact: Null (M4 chip absorbs overhead easily).