I used Bitdefender and found it missed a great many bits of malware that were picked up by Spyhunter and Clamwin. I removed it after a week and despite their 30-day guarantee it took more than a month and my filing a dispute with my credit card company to get it resolved.
Malwarebytes is a similarly bad company with automatic renewal charges and ineffective software.
I use the free Clamwin for antivirus, the free Comodo for the firewall, and the expensive but very capable Spyhunter for removal of adware. I need all three despite using Noscript and Ghostry on Firefox. They help but are not 100% effective at blocking all adware tracking. I also do not use Facebook which is one of the very worst at tracking all your activity until your computer is shut down.
A Windows PC running the stoneage Microsoft Windows operating system costs me an extra $100 a year for the anti malware protection and an extra half hour a day of scanning and removal. Anyone who thinks that a Windows PC is cheaper than a Mac is ill informed.