Just for anyone running across this later, another limitation of the EzFJr is that you have to load a custom F/w if you want SGB to work. The Krykzz cart works fine out the box for both platforms. That said, I do own both, and the EzFlash is a great budget alternative for handhelds if you can get it.
Quite an oversimplification, but it hit some of the high points. It’s a good little opinion piece, and worth the time, I think.