It also bears repeating the old design adage: "Less is more."
More is not always, or even often, better once a sufficiency is present. Having one firewall, one security suite, and similar is generally best practice. It's fine to have multiple tools, if you so desire, that run strictly on-demand, but not to have multiple tools trying to run realtime protection at one time.
Not only do they often end up engaging in "a fight to the death" of the system, but even if they don't there's a big waste of resources with very little to be gained for it.
The best defense is developing safe habits for interacting with cyberspace. Most infections (regardless of whether by virus, malware, adware, spyware, etc.) come about as the result of...