King Dugan's Dungeon is the one you should probably play first, at least in terms of official releases. Well, from what I gather. I'm still plugging through it myself!
Apparently, JtRH is not quite as difficult, but has a few more features and gameplay mechanics.
But King Dugan's Dungeon is a great dungeon, and probably what a lot of us think of when we think "
DROD."
I'd go for that one first.
Also, the reason it is called 2.0 is because there is an older version, called the Architect's Edition, which is freeware. New features are added in the 2.0 engine, such as being able to hit backspace to undo a move. Perhaps Beethro learned a bit of precognition? Anyway, it certainly helps a lot, but might not be used by the vets. ("
When I was your age, we died 500 times on the same tar mother and begged for more!"
)
____________________________
-Chinook