Good morning, Here in England we have a magazine called "Which?" and they are very good with comparing different services. In a recent edition Firewalls etc., and the official windows Defender came out on top of their survey, my daughter has never used any thing else but Windows Defender and has not had any trouble at all. On the purchase of a new computer running Windows 8 I have not downloaded any third party defences and will continue in that until I come across any thing doubtful.
Very best regards from Keith in Derby England.