DD crunches numbers, the PD articles insert some reality and talk about draft strategy.
Always taking best available player will give you a pretty lousy team. Do you want to force 3 RBs in the first three rounds? How do you need to adjust the rest of your draft. Do you want to jump on the top defense, and what does that do to the rest of your roster? To Gates or not to Gates?
It tries to quantify a LOT of things, but will still do some crazy things. For example, I just did a mock where it took Brees in the 3rd round, then wanted me to take a backup QB in round 6 (even though it had the "need multiplier" set to 0.5 on QB).
Of course, if you just use DD then it will be Henderson & Dodds' fault if your team sucks