Something that turned out really well for us and isn't always considered is the potential for food prices to increase by the time you arrive. We bought the Dining Plan prior to the big October 2018 increase, so when we were doing the comparison math, we were calculating with July 2018 menu prices. What looked like a good value for us at July 2018 prices turned out to be a HUGE value at January 2019 prices. And don't forget to calculate the tax. You're paying tax out of pocket but not paying tax when using a credit.
After 4 character meals (Tusker House Rivers of Light Dining Package, Akershus, Hollywood & Vine Fantasmic Dining Package, and Crystal Palace), one Signature (Jiko), alcoholic drinks across the board, never once using a QS credit on a kids meal, and using a TON of snack credits at the
Festival of the Arts ($11.00 ribs for a snack credit!), my post-trip math calculated that we consumed $1,860.60 worth of food and drink for the $1,241.60 we paid into the Regular Dining Plan for 2 adults + 2 kids for 6 nights (i.e. we cleared $619.00 of "value", and now that I look at those numbers it's a weird coincidence that the cents column came out to 60 cents for both).
Normally, we're very frugal eaters at theme parks, and rarely drink. We live in SoCal and pack PB&J sandwiches and bring juice boxes when visiting
Disneyland, Knott's Berry Farm, Legoland, etc. We certainly could have gotten through our WDW trip spending WAYYY less than $1,241.60 if we wanted to. But for us, getting the Dining Plan was like eating on a cruise. Eat whatever you want, whenever you want, however you want, without worrying about how much it costs. Go ahead an order a cocktail with dinner. I'm not driving home! We're on vacation!