Hi,
Regarding the different SF2 soundfonts from Creative:
1. 28MBGM.sf2 has one of the biggest bugs ever made in an 'officially' released soundfont by Creative/Emu. Namely it completely misses Picked Bass (34) preset from the capital tones. So its usage is absolutely not recommended. Its characteristics is almost the same as the 4/8 MB soundfonts (but has more serious bugs) and there are much better sounding/less buggy soundfonts in the ~30MB range. It has only 135 presets (missing Picked Bass and no GS/MT-32 variation tones at all but it has 8 GS drum kits). Considering its size it is a rather mediocre 28MB soundfont.
Here is a test file attached to confirm the above bug:
download/file.php?id=129937
2. 8MBGMSFX.SF2/CT8MGM.SF2 (exactly the same one) is somewhere between the above and the 4MB one: it has 137 presets (so no GS/MT-32 variation tones at all, but has 9 GS drum kits). Compared to the 28MB one at least it has fully implemented capital tones (Picked Bass is not missing) and also has SFX Drum set at program 56 on channel 10. Otherwise it also has the same characteristics as the others.
3. 4GMGSMT.SF2/CT4MGM.SF2 (exactly the same one) is a decent 4MB SF2 soundfont with 329 presets (full GS variation tones and Drum sets + MT-32 tones and Drum set) . Arguably the 4GMGSMT.SF2 version is the most feature rich since it contains the most variation tones and drum sets.
All the above SF2 soundfonts have rather serious instrument range definition bugs. Try them e.g. with Storm.mid from Duke Nukem3D. The cricket mimicking effect is completely missing at the beginning:
download/file.php?id=129928
A decade ago I fixed some bugs in the 4MB one since it was the most feature rich and had the best performance/size ratio:
download/file.php?id=129934