When comparing MplayerX vs IINA, the Slant community recommends IINA for most people. In the question“What are the best video players for macOS?” IINA is ranked 1st while MplayerX is ranked 6th. The most important reason people chose IINA is:
It's like mpv, just more user friendly GUI and more settings available via UI.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Pleasant Mac Style view
MplayerX fits in OSX environment perfectly with it’s hot keys and plain, but stylish design, giving pleasure to work with
Pro Players “memory” of a last reproduced file
If turned off, player will start file reproduction from exact spot it was interrupted on
Pro Smart-play or automatic next video file search
For example, if number of files with sequent names are mashed up and thrown in the playlist, MplayerX is able to reproduce them in right order
Pro Smart multi-touch control
Convenient track pad commands, that allows user to toggle full screen, change frame size, aspect ratio and volume. To learn more, watch an easy and understandable "how-to" youtube video in the sources.
Pro Compatibility with other Apple products
File reproduction can be controled with an Apple remote, that awards user with more freedom. Furthermore, dirrect pass through is possible. Start streaming, connect and enjoy your home theatre
Pro Softwere was designed specially for OS X
As OS X is the only supporting system, the amount of bugs and problems is minimized. This also means, that player can play .m4p, .mp4 & .mov video files.
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
Cons
Con System crash is more frequent
MPlayerX creshes occur more often than in usual video players. They should be tackled properly.
Con High CPU usage is possible
Sometimes after the player or OS X update file reproduction can demand a significant part of CPU usage
Con No proper playlist feature
In spite of easy and comfy smart-play, in general playlist isn’t user friendly
Con No retina display support on old OSX
MPlayerX does not support retina display on OS X older than Mountain Lion, but amount of Mac’s with older OS X are quite rare nowadays
Con Unstable
May crash unexpectedly, while clicking on something in the subtitles section in the right-hand panel, for example.