OnionOS changed my entire mindset about what a retro handheld should be. I have an Anbernic 351m, Retroid 3+, and now a mini.
The mini, despite being technically inferior is by far my favorite because of OnionOS. Being able to turn it on, have it start right where I left off, and then ignore it and it completely turns itself off- not sleep makes it so easy that I play it all the time.
Retroid means Android which means it sleeps instead of powering off. And fill power on is slow. And configuring a Game Front End is always extremely time consuming.
Onion just works. If they added a single Thumbstick to the Miyoo, it could handle N64 and I wouldn't need anything else.