When I did my comparisons on DDP, I compared only the TS meals we would have actually purchased, less the DDE discount + tax and tip, vs the cost for 2 adults and 1 child. In a five-day trip, I calculated that we saved $70 with DDP, assuming that all the CS and snack credits were just bonuses. So even with that very conservative approach, we came out ahead with DDP.
However, we are DVC members, so we're not paying a higher room rate, nor do we have to figure in the extra park tickets.