We've used both and enjoyed both, but I think you really just have to get the facts on both options and do your own math to see which is better for you.
I think it is important to do your financial calculations in a realistic manner, rather than comparing the cost of DDP to the menu prices, for example.
Your true cost for DDP is any premium you have to pay on your room rate (might be none, might be significant, depending) + the cost of any tickets you are forced to purchase which you don't really need + the cost of the DDP.
I would compare the full price of the DDP to the actual food budget you would anticipate if you were paying cash -- not the inflated menu prices of stuff you would never order if you weren't on DDP.
The true cost of the DDE (assuming you are not a Florida resident) would be the difference between the price of the AP and the ticket you would normally purchase + the price of the DDE Card. [ETA: Keep in mind you only need one AP to be eligible to buy DDE.]
There are several huge differences between the DDP and DDE card.
The DDE card is good for about 13 months from the time you order it (the CM will be able to tell you exactly) vs. DDP being only for the length of your stay. So, depending on your visitation pattern, you might be able to use it for more than one trip. We used our DDE for three trips in a 13 month period.
One DDP person's credits are obviously only for that person, but the DDE card can be applied to up to ten people dining on the same check. That makes DDE very handy if you are dining with other people, especially if they are not on DDP.
The DDE card gives you a 20% discount, not only on food, but also on beverages...including alcoholic beverages. DDE is the only discount plan that applies to alcohol.
DDP obviously can be used for any meal and many snacks; DDE is mostly used at TS locations, as noted above.