I am one of those people with MANY top-of-the-line sound modules, and generally I prefer the sound of those MIDI modules over Real Tracks, Not to mention being able to easily edit MIDI tracks. I frequently slice & dice real tracks in my Sequencer, but that's another story.
Real Tracks are great for quickly putting together a professional sounding performance, but when I'm polishing that "Fabulous New Song" I go with MIDI as much as I can.