Let's start off with the obvious question: why should you care? Well, do you like DOS games? Would you like to have really high quality music in your DOS games? If the answer is yes to these, then you should definitely care.
As an example of the difference this can make for General Midi games, check out these two clips. The first is using Adlib/Sound Blaster audio, and the second is using the FluidR3 soundfont (which we can use with VirtualMidiSynth).