This is a case that we thought can happen in theory (not sure if there is already a real one before). The reason is that citra is using GPU in an uncommon way comparing with normal PC games: it transfers texture data between general RAM and graphics RAM a lot. In this process, an integrated GPU, where the transfer distance is "short", can probably perform better than a discrete GPU, where the distance is "far".
Can it be done so that it will use the GPU ram directly in the future? I wish i knew how to do it myself
Thanks