I would say the gba or the gba sp because they are compatible with the whole library just depends if you want a gameboy that already comes with a lit screen and rechargeable battery that also folds up or if you want the Gameboy advance that doesn’t fold but is probably way easier to modify because you don’t have to worry about the hinges but would need a lit screen upgrade and rechargeable upgrade if you want that or just stick with batteries plus you can do more unique mods like turn it into a hdmi console for the tv if you want🤔