You don't seriously think you'll get an objective opinion on Windows Defender in a forum sponsored by Microsoft, do you?
Windows Defender is fine antivirus software, but lots of third-party developers also make excellent antivirus software. It's your choice to make - no one can tell you what is best for you.
When I made my choice, I preferred to rely on objective testing rather than the opinions of people I never met whose expertise was unknown to me (and easy to exagerate.) The professionals who test antivirus software for a living are the real experts ... I turned to their testing results for my decision.
If you do the same, you'll find that, while on any given day there are some products that are better than others, on the whole most antivirus does a fine job of defending a computer against malware. So your choice may be heavily influenced by how easy it is to work with the software, whether you like the user interface, whether you get good support and what other features come with the software. These are choices only you can make, after considering the facts.
Most important of all is to appreciate that antivirus software is only a second line of defense against malicious attacks. We, the computer users, are the first line of defense - our willingness to learn about the threats that face us and how to avoid them. No antivirus software can do that.