Now, the general consensus is that they should be changed gradually, rather than all at once. Some obviously bad keybindings have been removed this way (eg. Esc->quit.) If you create an issue for your most hated keybind, it can probably be changed.
I know I should probably raise this on the Github issue, and I'm posting this without having even looked at MPV yet to see if this is how it's already done or if there's any issues with this approach, but why not take the approach of 'profiles'? Ship with (at least) 2 profiles baked in - 'MPV legacy' and 'MPC-style'. Add more as desired. That way those who simply want to jump to a familiar system can choose MPC-style, those who want to stick with what they're familiar with from using MPV can, and the rest can customise as desired.
Any gradual changes just mean gradual changes to a keybind file. Anyone who doesn't like them can simply use their own keybind file from previous versions, or from their own modification.
Though rather than being baked in, these bindings have to be manually copied over the user's input.conf. mpv's config profiles don't extend to input.conf at the moment.
I find MPC key binding a lot better than VLC. I use skip ahead by 10 seconds a lot and using simple arrow key on MPC is very convenient compared to VLC where you need to hit a combo every time.
SMPlayer can barely even be considered an mpv front-end and I hope nobody who uses it will ever make an mpv bug report again. It's a gigantic pile of hacks from the MPlayer age, and it “interfaces” with mpv using the most horrible method possible (embedding the mpv window and sending keystrokes to it)
Perhaps from the implementation standpoint, but from the user standpoint it's second to none. For example, it's the only one I know that supports dual subtitles (--secondary-sid in mpv). For more advanced features, it also allows you to pass CLI flags to mpv, e.g. for things like `--video-stereo-mode=sbs2l` (subtitles and UI for 3D videos).
Also, enable "Run mpv in its own window" under Preferences -> Advanced. This removes all the issues caused by the default mode of embedding the mpv window (such as subtitles being on the video and not in the black bars).
Now, the general consensus is that they should be changed gradually, rather than all at once. Some obviously bad keybindings have been removed this way (eg. Esc->quit.) If you create an issue for your most hated keybind, it can probably be changed.