Gameplay isn't just about making certain shots; it is how those shots combine to reach certain goals. To me, the pre-DMD pins didn't have enough to do. They were still fun, but the DMD games are just a more complete experience. It isn't just the display that makes the difference though; there is just more to do on the newer games.
I think it is weird that DMDs are still used though. They just seem really expensive for what they do. I think something like the ColorDMD idea would be best. It is an LCD, so you could use it that way, but it also works as a DMD.