>>1229737The standard Gameboy Advance is probably the peak of ergonomics and has a good size screen, but the Micro is great for its portability, the fact that it can fit in your pocket and leave plenty of room for other stuff.
Downside for the GBA is that it doesn't have a backlit screen, but if you want to shell out an extra $40 or have a backlit GBA SP you dont care about you can easily make a backlit GBA.
Downside for the Micro is the battery, but if you have the ability to recharge and youre worried about old internal batteries Nintendo products have plenty of quality aftermarket parts.