Hello MikeRuthThere is no universal "one size fits all" solution
that works for everyone and there is no best anti-virus
.No single product is 100% foolproof
and can prevent, detect and remove all threats at any given time. Just because one anti-virus detected threats that another missed, does not mean its more effective. The security community is in a constant state of change as new infections appear and it takes time for them to be reported, samples collected, analyzed, and tested by anti-vendors. Security vendors use different scanning engines and different detection methods such as heuristic analysis
or behavioral analysis
which can account for discrepancies in scanning outcomes. Depending on how often the anti-virus database is updated can also account for differences in threat detections.
With that said, there are some suggestions and recommended security tools to supplement your antivirus provided in this topic
If you are repairing computers for customers, there is not much you can do if they do not take the time to educate themselves in order to prevent malware infection. I would ask them to read How Malware Spreads - How did I get infected
which explains the most common ways malware is contracted and spread.