This is a HiDef-derived Soundfont specifically geared towards the SC-88Pro MIDIs from the recent Pokemon Emerald source code leak, MIDIs which are far more accurate than even ROM rips, especially the instrument choices. The drums are from Charm by Strix Soundfont Team, with a simple re-arrangement of a few samples to make them work properly. The GB Channel 3 waves are from GXSCC, and were picked to specifically match the waves that RSE and FRLG use, except that GXSCC is double the bit depth, which makes this nice (although the GBA's GB channel 3 can do double the sample length, 64 instead of 32.)
What this all means is that the Roland instruments and the GB Ch3 waves are both far better quality than the real GBA, even with AGBPLAY output, and more accurate than a ROM rip could ever do. Also, the MIDIs this is for are the leaked MIDIs, which means that these are the best quality possible on all counts, whether it be instrumentation, GB waves, Roland waves, mixing, arrangement, and the like. I, stgiga, will be doing an OpenMPT oscilloscope view series soon after my college workload lightens.