In order of purchase, I got the:
SNES Mini (US)
Mega Drive Mini (JP)
PC Enigine Mini (JP)
Still have my original SNES at my parents, and I typically do most of my emulation either through the PC hooked up to the TV, or a raspberry pi setup hooked up to CRT’s, but I got the SNES mini because it was a cool way to get a never officially released version of Star Fox 2, and I liked the menu music and how cute the small form factor was.
I love Sega, and the Mega Drive will pretty much always be my #1 favorite piece of hardware of all time. I own a model 1 Genesis, which, like the SNES, is still at my parent’s place. This one had some rare/unusual titles on it, though, and I never owned the cooler looking Mega Drive (I like the color combos more, and the box is rad). Anything M2 is involved in I feel compelled to support, as well. The UI is fun, and the music is cool, and the silly attention to detail on the hardware is still the best out of all of them.
Never owned a PC Engine/TG16, and have only experienced it through emulation. They’re still at pretty ok prices when I spot them on my trips to used games shops, and I’m still thinking of grabbing some real hardware at some point, but just like the Mega Drive mini, I was drawn in by the very obvious love and attention to detail that was put into specifically the software for it. More M2, fantastic menus and music, the ability to swap between all of the menus despite the hardware, and it’s a really solid introduction to the system.
Over all, it’s a novelty/toy collector thing for me. I love how they look, the USB game pads feel great, and the software presentation is really cool. It can be fun to have something “just work” with a nice presentation, even if I have a pi, or a PC that can practically play any previous generation system. I’m also more into the idea of getting one if “M2,” or, “rare/never officially released,” are mentioned for a game that’s included.
Edit: One additional thought is how much better the MD and PCE feel over Nintendo’s entries. I love that the MD Mini actually gives you a brief description/release date when selecting a game (and even arrange the games by the spine of the box), and was surprised to not see that on the PCE. PCE makes up for it, though, by also having PCE CD games available to play, and little PC engines dancing around the menu the whole time.