The specifics of the Universal all day dining plan have changed since I last visited there in January 2012, so I can't comment on that.
Aquatica's all day dining is an excellent value, but the food is nothing special. Its comprised of a roster of limited but universally-appealing selections....pizza, barbecued chicken legs, hot dogs, watermelon, brownies, etc. All food (beverages excepted) must be consumed within the restaurant boundaries....no taking your meals back to your beach chair or cabana. At $15 the pricing is excellent and you can come and go as many times as you please, which is a real plus. You can add a refillable sports bottle for $5, which again is a great value. The food is perfectly palatable but definitely doesn't measure up to the offerings at the Waterstone Grill (the a la carte restaurant on site). We have done both dining options (the Banana Beach Buffet and the Waterstone Grill) and while we strongly prefer the food at Waterstone vs. the BBB, the value of the buffet and the all-day dining is hard to ignore. We have already purchased our Banana Beach vouchers for our August trip (they were only $12 pp on SW's Black Friday sale........where else can we eat all day for $12 pp???). I believe the restaurant opens at 11 am, so you will have to eat breakfast before you arrive.
SeaWorld's all day dining is fantastic. Truly unlimited, breakfast right through until 30 minutes before the park closes. You are entitled to one entrée, one side (dessert, salad, fruit, fries, a pickle, etc.) and one drink each time through the line. Or you can do any combination of those if you don't want all 3. Food options are vast (barbecue platters, pizza, fish & chips, fettuccini alfredo with chicken, turkey bread bowls, wraps, chicken tenders, etc.) and we have found food quality to be consistently great. Our favourites are Voyageurs Smokehouse for BBQ and the Seafire Inn for "sit down" type meals, and Mango Joes for Quick Service. Its wonderful to be able to grab a cold bottle of water anytime you want it, especially if its a warm day.....and my guys love being able to grab a slice of pizza or an order of chicken strips between meals if the tummies start rumbling. If you are spending the whole day at the park, I highly recommend the SW dining

. I've already pre-bought mine for August!
Just a side note....the refillable sports bottles can be refilled for the same cost (99 cents, IIRC) at any of the parks. So you can buy a refillable bottle at SW and refill it at Aquatica, BG, Universal, or IOA. Or you can buy a bottle at Universal and refill it at SW, Aquatica, etc. You can bring your cups back year after year and you don't have to pay a fee like at Disney to reactivate your cup

. Popcorn buckets follow the same premise .... buy at one park and you can refill it at the others

. So those can be a GREAT value too!