my 2 cents
QSDP : not working for us with a 4 year old. Food is always the same off the kids selection.
DDP : I'd rather carry a huge boulder in my backpack all day than being tied to a fixed seat down meal everyday. I know it gets you to cool off a little and rest. But I think one of the thing you can't plan in advance is the moment your party is gonna crash.
It happened to us quite a few times when we had ADRs in parks. We were all full of energy, asking for more, but had to stop for a sit down meal. As a result, we ended up having no more energy after the meal, as we had cooled off too much) and ended up going back to the resort, and eventually lost half the day doing nothing.
DxDP : Even worse than above.
We do sit down meals, but only as character breakfast as a way to start an "offsite" day, such as picking citrus at a citrus farm, setting off to KSC, or idling around the pool at the resort, or for dinner at the end of a long day at the parks.
But to do that each and every day just does not suit our way of doing Disney
In the end, it's different from guest to guest.
What's good for you may not be good for the next person.
All we can do is give advice based on our own experience and likings.
Now as for the topic's title : is DxDP worth it ?
well ... how comfortable are you with the idea of spending 4 or 5 hours a day on restaurants ?
It might be worth it if restaurants are your kind of holiday (some like that)