We are personally fans of the dining plan (1 TS, 1 QS, 1 snack) because it is convenient and more than enough food for our family. We like it because we don't have to worry about paying anything extra for food once we are there because this plan keeps us more than full enough. It's fun to eat at character meals and not worry about the bill (but, remember that tips are not included in the cost of the meal and the tips really do add up).
Many people think it's not great value, and I see their point of view. If you are doing it to save $, it's probably not going to be helpful. But... if you want a stress free vacation (let kids order whatever they want, regardless of watching the price listed) then dining plan has value (this is how we see it as we only go once a year, so it's our splurge for vacation).
If you are planning on bringing in food to your room, you will want a place with a kitchen (we only ever stay in regular resort rooms and fridges are not big enough to hold much food).
We also bring bagels, cereal, granola bars to help cut down on costs. We fly to Disney and do not have a car, so we can't just go grab food off of the resort very easily.
I think the dining plans vs grocery delivery is very subjective - keep reading things / researching and then make your own decisions.
Have a great trip.