I have ran both single pipes. The motofast was cool back in the day, but thats before pro circuit was even making a banshee pipe. Lets put it this way>
Old bike with +6 swingarm, all built up for sand with a motofast pipe was decently fast. You had to pop the clutch and pull on the front end, then it would wheelie.
My current bike with a +6.5" swingarm, all built low-mid for sand with the pro circuits, the front end is always up in the air. I feel my current setup makes the most torque out of any setup I have ever ran.