Windows Defender is quite light and works wonderfully (besides the slow scanning of files when you first open up the file explorer). I'm just using all built in Windows security features (Applocker, Windows Defender + Firewall, UAC on max) combined with HitmanPro.Alert and Malwarebytes free. I have no issues at all with malware. I've tried to purposely infect myself so many times and I fail every time.
Avira is quite light but I had to stop using it cause it always caused my audio to start cracking and hissing and skip while playing music through headphones. I have no idea why. The problem is solved as soon as I removed it.
Avast is just full of ads and used to be my go to but now it's just full of ads constantly popping up on you and you could disable it using game mode but I like to know what is going on.
AVG is just bad. The detection rates are pretty low but are probably higher than Windows Defender. I haven't used it in ages. Prob since the 2011 version. So I could give it a go again once the new 2016 version is out.
Panda free is nice but it is cloud based and I couldn't get the URL filter to work with Edge and you need to install the Yahoo toolbar to get it to work.
360 TSE I've had such issues like false positives and random system slowdown and the UI just being really slow for me and the detection rate was pretty bad on some files and it had a detection ratio of like 40 on virus total. It was pretty sad to see many times.
So ya. I've had almost every free AV and Windows Defender is built in and just works without any hassles and updates all on it's own with Windows update.