M.S. Windows Defender is touted as being as good as the rest and its free.(built into Windows 10)
However, I have all my Windows 10 updates either turned off or delayed...this would affect Windows Defender also...so I dont use it.
Bitdefender is light on the system and is highly rated.
I use Bitdefender Free.
I also find Windows Defender a bit on the annoying side to configure folders and files to be protected from a scan.
As in , certain folders and files not to be scanned.!
I use MS Windows Defender