Wow, more than 2 years on, this thread is still active.
With my new Windows 10 laptop, after 2 years on the old desktop with Bitdefender paid-for, I am using Windows Defender with Windows Firewall and am about to install Malwarebytes 3 Premium.
This is after discussing the options on various Forums.
On the old desktop, I got into a "computer slowed down till it almost stopped" thing with Bitdefender Total Security.
So thinking that the old desktop was dying, I bought the new laptop.
Then as an experiment I uninstalled Bitdefender from the old desktop and went with Windows Defender and Malwarebytes 3 Premium trial. It was like a new computer again. However the new laptop is faster and handier, so I am still retiring the old desktop.
The combination of Windows Defender, Windows Firewall and Malwarebytes 3 Premium seems to get a good press.
But it all seems to be a bit like betting on horse racing . . . .
I have learnt to take great care that all these security apps are kept right up to date.
Mike