The answer is that it depends on your family and how you like to eat. My sister and I have different family sizes, different preferences, etc. We each plotted things out for our vacations (both have DVC as well). Amazingly, it came out really close for
DDP vs. DDE for both of us.
In my case, I hav a valid DDE from a previous trip. I decided to purchase the DDP this trip so that we can/will go to some different (read that more expensive) restaurants, and I won't cringe at what DD orders. She is a teen and tends to go expensive. While the cost will be about what I would have spent with DDE, the DDP gives me more emotional freedom!
Sis and her family like to do character breakfasts and signature dinners. Their DD is on child's rates for the breakfasts, and shares their food for the dinners (or orders off the inexpensive children's menu). They don't like counter service. THus, for them, the DDE was the better choice. Again, she felt that the cost would be almost exactly equal, but the DDE fit their lifestyle better.
SO...it depends on what works for you. IF you like to do one TS, one CS per day (or it averages to that over your trip), the DDP is great. DDE doesn't apply to most CS, so if you like CS, it might not be the best. Using 2 TS for signature restaurants might not be the wisest use--that can be cheaper on DDE. You really need to work it out based on your family and how/where you like to eat.