Fran, UD, Donny, and others using Mp3 + SMFs

If you are set up for both Mp3 and SMFs off you laptop, is the SMF superfluous? That is, with the ability to incorporate audio with the mp3, but not with the SMF, plus all other advantages of the mp3, can you see any advantage of still using SMFs rather than converting everything to mp3?

The only reason to keep files in SMF format would be to save space, or play lyrics, or send the midi signal to a keyboard for improved sound quality. I'd like to slowly change all my "go to" midi files to MP3, and add backing vocals on all of them. That way I can have "my sound" using an acoustic piano or guitar as my main axe.
I'd be lost without the harmonizer, so I will convert as many as i can....a little at a time.

That makes sense, because it's kinda the way I've been thinking.