When comparing Splash vs IINA, the Slant community recommends IINA for most people. In the question“What are the best HEVC/H.265-capable media players?” IINA is ranked 6th while Splash is ranked 7th. The most important reason people chose IINA is:
It's like mpv, just more user friendly GUI and more settings available via UI.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Image Processing
Pro Audio bitstreaming support
Audio bitsteaming to external audio amplifiers is easy to set up and works for all major HD audio formats, such as Dolby, TrueHD and DTS HD Master Audio.
Pro Motion / frame interpolation
This is a great feature that works out of the box. Videos are MUCH smoother because of this.
Pro Hardware support for decoding
Hardware decoding for AMD, Intel and NVidia GPUs including iGPUs (integrated GPUs).
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 Can't display properly .srt html subtitle
Con Unstable
May crash unexpectedly, while clicking on something in the subtitles section in the right-hand panel, for example.