I agree with the pp who pointed out they are different experiences. If you like, you can click on my TR below - I have links to my DC day.
At DC it is a whole day experience mostly outside in a beautiful beachy resort. The dolphin experience is 45 minutes (15 education 30 min with dolphins) of it. Then you have all your food (continental breakfast, nice hot lunch), snacks (mostly mediocre prepackaged stuff), and beverages. You can also wade with, touch, and feed the stingrays, snorkel in the tropical reef, enjoy the huge lazy river (this is freshwater, the rest is salt), and spend time in the aviary watching and feeding the birds. You can up the intensity of the animal interaction if you do the trainer of the day package (expensive!)
For the dolphins in depth tour (I haven't personally done it) I would encourage you to search it on the TR board including the completed TRs. I'm pretty sure I read someone elses descriptions and photos. Dolphins in depth is 3 hours, indoors, and the dolphin interaction is if I recall others' descriptions about the same length at DC. You may get to try out a training activity. Overall, you seem to get a more concentrated educational experience, whereas at DC is it more relaxed and laid back.
Please post here if you do it!