On Tapatalk, so keeping it short.
After playing them:
No headphone jacks on either the arcade or game gear style.
Controls feel better than expected.  
All the games I tried so far on the arcade one suck pretty bad.  Most are a single play field.  Some are stupid simple, like a dinosaur catching falling balls.  
The games on the game gear style one are a bit better.  They kinda look like generic NES games.  The control is only 4-way.
Conclusion: The games aren't worth anything.   The cases are worth it for hacking or decoration.
I saw a teardown of the arcade one.  The screen is mounted on the main PCB, so I think it would be a PITA to reuse.  The housing and controls are very nice though and on a separate board.