As for the disney plan, I've had great luck with all the restaurants at Disney I've been to other than the Pepper market at the Coronado springs resort. (And that was really an off hour, so that might account for the poor food there.)
I don't know if you can still do it, but there used to be a way to manipulate the disney system if you had kids. The number of meal 'Tickets' was assigned to a room, so if you were two adults with two kids, you had 4 'tickets' for meals. If you went to the nicer restaurants that require two meals to eat, you could use the 'kids' meals for the adults and buy your kids something inexpensive off the kids menu. I don't know if this loophole is still there, though.
Also, I have not used Universals plan, because the value is not there during the off season when they close early. I typically only eat one meal during the day, and without a drink included and the limited choices, it has not made sense.
I might look into the SeaWorld package, but again, I don't think the numbers add up if all you eat at the park is one moderate lunch and one dinner. Plus, I like the ribs. :-)
As for Disney, again, you're going to end up paying out of pocket pretty much whatever plan you choose (minimizing the convenience factor), so unless it was a free throw-in on my vacation package, I'd rather pay my own way and have complete flexibility in ordering, with no chance of paying for something that I won't use.
If I were someone with a big appetite for burgers, fries and counter-service food, of course, the math would be different and these could be great deals. But that's not me.
I also have done Universal's meal deal in it's early days when nearly every restaurant was included on the list (minus Mythos of course). It was good, but by the end of the day you never want to see another burger and fry platter. We went about a year later and wow the meal deal was completely different. The food quality had greatly decreased and now we were limited to the 3 restaurants per park. I was very disappointed and didn't feel like I got my money's worth at all. I would suggest skipping the meal deal plan at Universal and spend your money on it at Sea World or Busch Gardens.
The places at Busch gardens have a lot more variety than the ones on the Universal plan, the Disney plan is only worth it if you plan on ONLY doing Disney AND having enough money to stay at their resort. Seaworld's is the same plan as Busch Gardens but we split that park over two days, doing short bursts and they also have Shark's Underwater Grill which is worth paying full price for.
The dining plan at every park just seems like too much food, and that's coming from a heavy eater.
On a side note, California Grill and Jiko, my favourite Disney restaurants, are included in the plan as two-credit meals. Even with the two credits, it's still cheaper than dining there without a plan (assuming you eat more than just an entree).
But it sucks 'cuz I eat frequently throughout the day and if I wanted to eat the "small portioned" food offered at theme parks, I'll most likely have to sacrifice savory-ness for small portions. Starch over sauce.
I was please with Sea Worlds Deal. I was able to eat little items at many different resturants as i travels freely around the park and did not feel I had to time my activities around locations like at Univeral. The best part about Sea World was that bottled water was included. I went in July when it was extremly hot. I stopped in some locations just to get a bottle of water. I feel I got my money worth because I probably would have spent about that much on just water during the day. A plus for this plan is also if you have kids. If they do not like something that they got, they can easily go back to the line and get something else.
I have never had Disney's plan since I live in Florida and never have had the oportunity to stay on property. I wish they did have one for passholders. I would eat more meals in the parks if I could purchase a package to go with my season pass. My sister's family did stay on property and had the meal plan. The only issue that they encountered was trying to get reservations. Their main meal almost evey day had to be breakfast because those were the only reservations available and they booked months in advance.
Disney world needs to have and option of trading out dessert for something else like an appetizer or something. We spent 6 days there this summer and I was dying for a salad!!!
I hate that the sweets are almost forced on you.