Had trouble signing-in, now I got 2 draft reviews above that need removing please
Windows Defender may have missed 20% of zero day malware samples a while ago, but in recent months it is nearly as good as the others. Coupled with a second lie of defence such as the equally free Comodo Firewall to stop unknown nasties slipping through and phoning back home, it's pretty much all anyone needs.
I've tried most of the AV / suites out there over the years and I've come back to using MS / Defender for the reason that it just works and with minimal impact.
In my own recent tests of trojan droppers embedded in docs, pdfs, etc, Defender has been spotting most of these whilst Bitdefender and Norton were missing them, confirmed by checking on Virustotal. MS may not be the best but they've come an awful long way and with an extra light layer such as CFW I personally think it's the best and reliable solution out there, had too many issues with all of the others I tried.