I only trust Windows Defender from Microsoft. 1 - They know the internals of their own system. 2 - They have strong interest in keeping your OS running well. 3 - it is free.
You could create a "Standard" account for your day-to-day. Then no need for virus protection. ^_^ To install software, you'll have an extra step of typing in the admin user name and password. Nice.
Avast free, but NOT for the antivirus. It has a really convenient software updating utility which will make you far more secure than any antivirus feature ever could.
Some of those with high detection ratios either (a) use excessive heuristics or (b) detect things that could be considered "riskware" or a "hacker tool", even if the software runs in the foreground and does not cause any problems for the user. Then again, if you never use "hacker tools", then it may not matter much to you.
After I stopped using Windows I've revisited my definition of "works well".
Not trying to troll or bash Microsoft here and perhaps you have strong reasons to stay on it, but sometimes people try to treat symptom not the problem.
Could it be that the "problem" in this case is that Windows has been so popular over such a long period? The popularity not only makes it a desirable target for malware but also makes it a desirable platform for cookie-cutter anti-malware programs, many of which are not worth the bits they are printed on. Another part of the problem is that many people are still running old versions of Windows (some even before User Account Control was implemented), which Microsoft is clearly trying to resolve here with the gratis Windows 10 upgrades.
