When comparing IINA vs MPV, the Slant community recommends MPV for most people. In the question“What are the best HEVC/H.265-capable media players?” MPV is ranked 1st while IINA is ranked 6th. The most important reason people chose MPV is:
When used with youtube-dl.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Like MPV with better GUI and settings
It's like mpv, just more user friendly GUI and more settings available via UI.
Pro Extremely stable
Extremely stable, even while still in the beta.
Pro Support for lots of codecs
Supports lots of video codecs, like mp4, mkv, etc, and lots of audio codecs including opus.
Pro Doesn't black out other displays when going full screen
It can black out other screens if you want, but out of the box it leaves your other displays alone.
Pro Runs on MPV so it's scriptable and runs any MPV script.
More information here.
Tip: if you're doing a lot of cropping and slicing of videos and you thought the new quick tools in Finder / Quicktime Player are a great improvement, try setting up IINA with slicing.lua and some keybindings for navigating your video + setting the slicing positions.
Make sure your ffmpeg command (in slicing.lua) is set to copy the original codecs and that it's using your GPU.
Pro Online subtitle searching and intelligent local subtitle matching
Pro Fully customizable keyboard, mouse, trackpad, and gesture controls
Pro Open source
Pro Powered by FFmpeg
Pro Integrates with streaming services
When used with youtube-dl.
Pro Needs no additional codecs
Everything MPV needs to play media files is contained within which means no outside codecs are needed.
Pro Minimal interface
Click to open files and get Video with sound (and passthrough of codecs like DTS etc) for a perfect cinema experience. Works okay for many files.
Default window is not much more than a title bar - and if you drag/resize the window it resizes the video and leaves no empty areas. There is no visible control or display unless you use mouse/keyboard over the window.
This is the best player to use unless you're going for a media center (then use MPV based Plex Media Player to display and play the Plex Server library).
Pro Up to date
Always up to date, rapid development.
Pro Extremely responsive
Pro Caches livestreams
Intelligently caches livestreams and enables jumping within the cached stream.
Pro Fast
Cons
Con Unstable
May crash unexpectedly, while clicking on something in the subtitles section in the right-hand panel, for example.
Con Blacks out other displays when going full screen
Con Minimal theme support
Con Lack of a typical GUI can be jarring to some
The minimal interface comes at the cost of beginner-friendliness. You need to know keyboard shortcuts by heart, settings are set in text files, right-clicking won't bring up a menu, etc.