Okay, I think I have figures this out, and in almost EVERY case,
Free Dining will save you more money - this is based on the limited information in your original post. You have stated that you will be at POR for 9 nights, and that you are intending to purchase the
DDP anyway. You did not give your party size, and since the cost of having a fifth person (using the trundle bed) requires a lot of messing around with my figures, I'm assuming that your family is 4 people at most, and since you said "we", 2 at least.
Secondly, depending on the ages, you can have any combination of adult and child rates in terms of the dining plan, while keeping the room rate constant. So, in my figures, when I say (for example) 3 adults 1 child, that could assume a child of 13 who has to pay the "adult" rate for the Dining Plan.
So, here are the figures.
For a "Standard View" Room
$149/night at Rack Rate with Free Dining = $1508.67
$149/night at a 40% discount and Paying for dining in the following combinations:
1 adult 1 child $1337.04
1 adult 2 children $1426.95
1 adult 3 children $1516.86
2 adults $1589.04
2 adults 1 child $1678.95
2 adults 2 children $1768.86
3 adults $1930.95
3 adults 1 child $2020.86
4 adults $2272.86
For a "Preferred View" Room
$165/night at Rack Rate with Free Dining = $1670.67
$165/night at a 40% discount and Paying for dining in the following combinations:
1 adult 1 child $1434.24
1 adult 2 children $1524.15
1 adult 3 children $1614.06
2 adults $1686.24
2 adults 1 child $1776.15
2 adults 2 children $1866.06
3 adults $2028.15
3 adults 1 child $2118.06
4 adults $2370.06
Green means stick with the 40% and pay for dining
Orange is basically a toss-up, but stick with the 40% to avoid having to change the reservation
Red means you will start to save a decent amount of money, consider changing to Free Dining.
Chances are, if there are at least two adults in your group, you'll likely want to change, except in the case of having ONLY two adults total in a Preferred Room.
As far as I can tell, I did the math correctly, including the resort tax rate. My figures are based on the following:
9 nights rack rate in Standard = $1508.67
9 nights rack rate in Preferred = $1670.67
9 nights 40% off in Standard = $955.22
9 nights 40% off in Preferred = $1002.42
Dining Plan
Each "Adult" (age 9 and up) 9 nights = $341.91
Each "Child" (age 3 to 9) 9 nights = $89.91
I hope this helps!