For my use case I don't often unhook the USB -- I just set it up once and forget about it. Or at least that would be the plan... I haven't had an opportunity to actually set stuff up on it. I was kinda scared off when the guide I was following showed a really long delay after adding a complete romset. I don't want to have a folder loading delay like I was seeing and have so far kept to the onboard storage. And I haven't tried using USB with retroarch yet.

I bought Fun-Home 2 Pack Left Angle USB 2.0 Micro Male to USB Female Host OTG Adapter and it seemed to work OK for my SNES and NES as far as physical connection. I can't really say for or against it just yet.

For the unit you have that you're unhappy with -- can you share more about that one? Make, model, where you bought it?