I have been using bitdefender and this AV is the best I used
I have tried AVG, Avast, kasperky, PC cillian, Macfee, Avira
Read the reviews and bit defender is always in the top three.
People talk about windows defender be good enough ( if you don't go to dodgy websites) but can get virus from usb sticks ( sharing ) , e-mails and also through Skype
Better to be safe than sorry I say