ZFR: I use FluidR3 because that's the one the author of the website said he's using. I remember trying some other one and it was just... too good? Made it sound more like an orchestra, not a retro video game.
Yeah it makes sense to try out different (popular) soundfonts to get one that sounds good to one's ears. It may also depend a lot on the games one is using for testing, some soundfont might sound more pleasant on certain game while another better on another game, because the games use different instruments or because they use different sound balance etc...
I am affected by having a real Roland SCC-1 (Sound Canvas) which I always used for playing General MIDI games, so I was trying to find a soundfont that resembles it (the instrument balance etc,), and also because I kept reading that for many DOS game General MIDI composers, Sound Canvas was the very MIDI synthesizer they were using, ie. with Sound Canvas you would get the music exactly as the composer intended.
Chorium Rev A reminds me somewhat of Roland SCC-1 (balance between instruments etc.), but it is better than a genuine SCC-1 which is not surprising because SCC-1, as well as other General MIDI sound cards of the time, were really restricted by the amount of their ROM/RAM.
Timbres of Heaven has even better quality instruments than Chorium Rev A (it is much bigger, after all), but in certain games I could hear its balance was quite different to what I was used to, like in the Tie Fighter intro music. I tried others as well (among them FluidR3, SGM and WeedsGM3), but to me they just sounded poorer and "wrong" overall. EDIT: It is interesting though that Chorium Rev A is considerably smaller in size than e.g. FluidR3 or SGM, yet I find its instruments more pleasant...
Yeah I've seen some others trying to find a soundfont that would sound similar to their SB AWE32 or Waveblaster, I guess everyone just wants what they were used to. Heck, some people even prefer playing their DOS games with Adlib/Soundblaster, because they were not used to hearing the music with Roland MT-32 or General MIDI.
ZFR: Incidentally, which soundfont would make it most similar to the generic MIDI driver that Windows 3/95 was using? Or would that be simply to use "Microsoft GS Wavetable Synth"?
I always thought that default Windows soundfont has remained the same, but I am mostly assuming. I find it lacking mainly because even though the description says it is a genuine GS/Sound Canvas soundfont licensed from Roland itself, it doesn't sound much like SCC-1 to me, and it seems to be lacking all the extra features that Sound Canvas had over General MIDI, and which many DOS "General MIDI" games utilize (like extra drum sets, reverb/echo effects etc.).