I think it's not so much that one sounds better or the other. The "uninterpolated" one is incorrect. The "interpolated" one is incorrect. The uninterpolated

I think it's not so much that one sounds better or the other. The "uninterpolated" one is incorrect. The "interpolated" one is incorrect. The uninterpolated one has sharp square edges, which isn't correct. The GBA has a 12dB/octave filter at around 12kHz (IIRC) on the output, which the uninterpolated simulated output doesn't appear to have. This would knock the corners off a bit and make it "smoother" and less hissy, but would still have quite crunchy low frequency sounds. The interpolated one smooths things off excessively, and while it doesn't really have much less spectral energy high up, what's there is in the wrong place.