When comparing µTorrent vs IINA, the Slant community recommends IINA for most people. In the question“What are the best Mac OSX apps for someone that's new to Apple?” IINA is ranked 16th while µTorrent is ranked 27th. 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 Lightweight
Weighs just barely over 1MB. And while it's gained a bit of feature creep over the years, it's still a lighter-weight client than many of its competitors.
Pro Full-featured
µTorrent covers basics such as Prioritization, Selective Downloading, DHT, PEX, LPD and Magnet URIs as well as Broadcatching, Sequential downloading and Search. It includes MSE/PE for security. It has graphical and web interfaces. Has UPnP, NAT-PMP, NAT traversal for automatic router configuration. Has UDP tracker and µTP data transfer protocol support. Even covers IPv6, web seeding, Embedded tracker, Super-seeding and proxy servers. And it auto-updates.
Pro Clean and easy to navigate user interface
A clean, visually-appealing interface that’s incredibly simple to navigate and cuts down on clutter by allowing any element of the UI not needed to be hidden.
Pro Doesn't slow down other Internet activities
The application automatically manages bandwidth it takes up to not get in the way of other Internet-dependent activities.
Pro Portable
µTorrent can be run without having to be installed as it stores all files and settings in the same folder. It can be put on an external storage device (such as a USB drive) and run directly from it.
Pro Built-in search
Built-in search engine allows finding torrents to download right from withing the torrent client.
Pro Cross-platform
µTorrent is available on Windows, Mac, Linux and Android.
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 Proprietary
No source code is publicly available. As such there's no way to independently check what security and privacy features are implemented and how as well as whether there's any malicious code or not.
Con No tracker exchange
Tracker exchange functionality allows peers to exchange information about trackers of a given file. It is another way of ensuring that the file is downloaded from the optimal source. µTorrent lacks this functionality.
Con Are known to bundle riskware
In additional to typical toolbar and ad bundles, µTorrent has previously bundled an automatic cryptocurrency-miner called EpicScale even if the user opted out of other bundled software.
Con Inappropriate ads (can be disabled)
Not only does μTorrent have ads in the free version, they tend to be inappropriate ads for scammy things like "meet russian women".
Ads can be disabled in the options. It's important to note that disabling ads (as well as all bundled software and featured content) can be a difficult process as it requires manually editing multiple key/value pairs in advanced settings.
The following keys have to all be turned to false by going to options > preferences > advanced:
bt.enable_pulse
distributed_share.enable
gui.show_notorrents_node
offers.left_rail_offer_enabled
gui.show_plus_upsell
offers.content_offer_autoexec
offers.sponsored_torrent_offer_enabled
offers.featured_content.badge.enabled
offers.featured_content_notifications_enabled
offers.featured_content_rss_enabled
Con Bundles bloat
Installation wizard starting with version 3 offers installing a variety of garbage features including toolbars and ads. And makes the process of opting out of such bundled software difficult. It's possible to find version 2.2.x online (1,2) - same lightweight, feature packed application without all the unneeded extras or ads.
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
