Yeah, they've added some confusion to the line up with that one. So they have the Digital 6 and the 6AL digital. Two entirely different boxes.
I had the Digital 6 unit in my drag car. It had built in dial controls for timing retard, staging rev limit, high rpm rev limit, nitrous timing retard and a few other features. Nifty piece. Worked great for about two years, then the rev limits switches freaked out. Couldn't rev over 3500 unless I cranked them all up to 10k.
Honestly though, aside from all the extra trick features, it didn't run any cleaner, mph any faster, or E.T. any quicker then the Jacobs system I had before it. i've since also used a Crane system and found the same thing. IMO, most reputable, brand name ignitions systems are going to give you very similar results and its only if you are capable of tuning things down to a very minute degree that you'll notice any great differences between them all. Although, one thing to consider with MSD is actually their name, Multiple Spark Discharge. This would lead you to belive that they provide an electrica storm or sparks, but once you reach 3500 rpm, they revert back to a good old single spark system like any other transistorized set up.