I’ve had less files that refuse to play using iina then vlc, also iina had none of that weird grey artifacting you get with vlc skipping/scrubbing through video (like actually how is that still a problem with vlc and vlc only). Those are the main technical reasons, but the ui is also much better/native feeling
1. Bluetooth audio does not play correctly the first second, often.
2. When pressing a random key accidentally, it is sometimes difficult to recover from the settings-change that it caused, and often a restart of the entire program is necessary.