Zonealarm been around forever... think i used most of the big packages in last 15 years. Norton, ZA, Avast, Kapersky, and now Bitdefender. I had Avast last but they always want you to buy more parts, Bitdefender just leaves me alone
Defender is better than nothing but I wouldn't only use it. its there for all those who don't even think of installing a Firewall or AV when using a pc