MIDI works well for me. I can lay down a number of tracks, and then play with patches until I find the combination that works best for me. Can't do that with straight audio.
I find that all my initial tracks are midi. I only start to get audio happening when I want to free synths up.
I also use MIDI to control my outboard effects, mixer, and convertors from my sequencer.
I can also use midi to have my other computer system play soft synths.
If you don't use synths, then maybe midi will buy you very little. But there are other uses.