Just get Avast and forget about it. They are all about as useless as each other, so don't agonize over it. The manual programs, such as Malwarebytes, are much more effective than the real-time ones, in my view.
There's a few ways to approach security programs. Obviously people that are gifted the nerd gene can get by fine without any, installing one only when the situation arises.
If you're relied upon to administer for users that DON'T have the know how to keep themselves and their systems safe, unfortunately even have a cocktail of Security Essentials + MalwareBytes doesn't help. I've found that, as far as commercial products goes, McAfee is the way to go for users like that.