DH by a long shot, unless the theme & unique plot/pinball combination of W?D will increase its enjoyment and longevity in your collection. The shots and ramps are more satisfying and varied in DH (third flipper and gun toy already mentioned).
You could argue that W?D has more to it from a choosing different strategic paths to scoring and progressing through the story line, whether to go for elevator floors (and which sequence) vs. interrogating suspects. Scoring imbalances aside, if you like gambling, W?D has a lot of opportunities for risking your points and for praying that the slots resurrect a lost ball, etc.
If you have a lot of novices who will be playing the machines, then W?D also comes with the feature of guaranteed play time (instead of 3 balls) for Novice setting, but I personally find this setting and framework annoying. I think there's something to be said -- even for beginners -- for appreciating only having 3 balls (for modern games) with which to play. And novices can simply press the Start button more often (for free, assuming it's for your home collection).