The advantage of riped originaly content ist to have well fretted songs and seperated tracks (Drums/guitar/bass).
Custom or selfmade songs were often well fretted, but without seperated tracks....... you have only one track.....
I did say it was not an optimal solution.It is one that has worked quite well for me when I had the .mid files and a crappy audio track (like the On Tour rips...) .
I do not care to have a track cut out on me when I miss a note (it's rather annoying to me and one of just many reasons I'd rather play FOF instead of my GH games or Rock Band).