I'll keep it brief and super unscientific, but my preorder for the Japanese version of the
Neo Geo Mini arrived (there's another world-wide release, still with 40 titles, but
with 14 different games).
The pro's: that joystick is pretty damn good, and playing fighting games using those controls work surprising well. If you want an experience closer to the arcade, the Arcade Archives/ACA versions with a decent fightstick is still superior, but considering the form factor it works very well.
Sure, there's a ton of King of Fighters and Fatal Fury, but there's also other gems like Blazing Star and Sengoku 3, as well as Ninja Masters and Twinkle Star Sprites. The Japanese version has Shock Troopers 2, with the western/world release getting the first Shock Troopers, so they'll be a slight reason to get both.
The con's: no internal battery. Neither the NES or SNES mini had one either, but they also didn't include a built in screen, so you'll still need an external power source for portable play (the spare USB port on my Switch does a pretty good job, and the cable is pretty long).
This is a slight criticism, but you'll have to apply the decals yourself. It's kinda strange considering the amount of work that went into the design of it, but I'm garbage at applying decals/stickers - struggle to keep things straight and without air bubbles!
The interesting: the emulation at least comes from a primary source, and it seems more based on the AES than the MVS version. When you fire up an AES cart in a Neo Geo, usually after pressing start the next screen will be an options screen, where you select the difficulty level, etc. (depending on the individual games, of course). And needless to say, those options in the MVS would be located in the soft-dip menu, which wouldn't be available to the public in an arcade setting.
It's not an issue: I think the point of the Neo Geo Mini is basically a 40th anniversary celebratory release, and it's pretty damn good (and modern save-states are always welcome). And there's little to no difference between the AES and MVS versions anyway.
I only mention it because if you are looking to the Mini for an "authentic, deathly historically accurate, definite" version of these games, this won't be it. The old games didn't have save states, but the NES and SNES mini took similar liberties by adding modern bells and whistles.
Okay, so this wasn't brief (

), and I haven't tested the HMDI output, and I don't have the controllers to test, so at least it's unscientific, kinda (

).
Edit: I paid ¥19,990 (so you run that through your relevant exchange rate), and I just had a quick look at eBay prices... oh boy... those inflated prices didn't take long to kick in! The official price (in Japan), minus tax, is ¥11,500, so...yeah...