free dining is generally better for larger parties. do the math, see what you would normally spend on eating. (don't forget to add in the tips! they aren't included anymore)
if you like to eat sit down meals a lot, and eat a couple meals a day it would be cheaper to do the free dining.
if you like to eat on the go, do mostly CS, you might be better paying meals out of pocket.
the thing I like about the free dining is I get to order expensive entrees I normally wouldn't. you have to look at what's best for your family.
one trip we purcahsed the quick service plan and Disney killed us!! we ended up with 3 quick service credits and a bunch of snack credits left over!!! (which I used for a bunch of crap to bring home )