First one only supports ROMs through emulation, the other two are Famicom and Mega Drive clones.
DX carries a GBA and GBA SP clone, both use emulation and are a bit crap but will work with some real carts. I bought the SP clone called Gamebox Advance a while ago, it's ok to experiment with but not a real substitute for a GBA (or GBA Micro or DS). I did a comparison of it with my GBA for a forum that eludes me right now.
There's also a set top box that runs the same software but with a slightly more powerful hardware variation so the GBA/CPS1/N-G emulation is a bit better, and it also has a GBA cart slot. I think it was called the V-Box or something.
All of those GBA clones have trouble running games with 3D and also wipe your save games if you use an actual cartridge.