Coming from someone who loves both games and owns one of them (Dredd) I would have to go with Dredd. ES is the game that got me hooked on pinball a few years back, but if you only have room for one game you'd probably want something deeper from the DMD era. Even if Dredd isn't exectly the deepest game in the world it still has a lot going for it between the modes and multiball - not to mention supergame gives you a quasi second game.
And the soundtrack totally kicks ass, too.