From what I've read Windows Defender has really turned around MS security reputation; its capable and current.
I did a lot or research before ditching other AV. My take back then is that it was almost as good, but way, way less resource intensive. And, in fact, it rescued an old computer that was just dying trying to run one of the famous AV suites... I forget which one. Anyway, I have just saved the money, both for the AV software and machine upgrades, and been quite happy ever since.
