I just wanna believe in that Microsoft Defender is enough for protection. However, I doubt that since it is so silent. There are no warnings for a long time, which makes it either suspicious as doesn't detect any virus or malware or superb antivirus which doesn't show useless alerts. I hope the 2nd option is true since I have been using for a long time.
I have test many of antivirus, at this time best detection and faster speed (lowest resource usage) is Qihoo 360 (for win10)
right today Defender did not detect an heavily pup loaded program I threw at it for testing purpose, had to use adw cleaner which did the job without conflicting
W10 10048 has uninstalled MBAM which was present (non resident) since W8 time. I installed F6Secure Ultralight x64 beta: it works like a charm, no conflicts, no resource hog, I suggest you give it a go
Defender is just a Microsoft software so not able to deal with Malwares ans spywares. Kaspersky in addition to Adwcleaner has been a efficient solution for a long time now.