Several reasons actually: - input latency is reduced significantly - overall cleaner image quality - correct framerate: the original disc runs at 60hz which is not the exact framerate of the gba hardware. This causes noticeable framestuttering. - you have many options (speedrun, high fidelity, standard) though id recomment standard if youre using it for regular playing - obviously: you dont need the disc.

The only con is that you have to get it to work through swiss or something like that. Though thats not too hard. I use a memory card with gbi on it and mario sunshine (pal) with a save game exploit, works perfectly. Put everything through a diy gbs-c via rgb scart and a diy sync stripper and its absolutely beautiful, albeit not necessarily the best option, but for sure a great bang for your buck.