How do you define "Best Value"?
Lowest cost? Delicious food? Great Entertainment? Awesome atmosphere? Combination of all? Do you want Table Service or Counter Service only?
Disney dining is very expensive. It is more expensive than what you will pay for off site. Counter service is clearly cheaper than table service, for the most part.
For cheapest way to eat, I would suggest a Counter Service lunch in the park of the day followed by an off site evening meal. That won't work though if you want to stay for night time entertainment. Then I guess for cheapest, you would need to do 2 CS meals at the park.
The Plaza Restaurant in the MK is a nice TS sandwich shop which is only a little more than the most expensive CS. It is nice to sit and be waited on and the sandwiches and fries are very good.
Cosmic Ray's Starlight Café, in the MK, has a chicken and ribs combo meal after 4 that is a good deal.
The chicken and rib combo at Flametree Barbeque in the AK is also a big meal.
In Epcot, the Tangerine Café in WS has a Sharma Platter that is also large and very good.
We always eat at 50's Prime Time Café in DHS. Definitely large portions, but not cheap
Good Luck