We ate at both last Oct, and there are really no differences in food, service, etc. between the two, IMHO. Outside of the volcano vs. waterfall theme, however.
But the AK RFC is better IMO because of location. We enjoyed AK all day, then hit RFC with the cool A/C and the tropical theming. It was a great finish to the day.
In DTD, RFC is just another theme restaurant among many, in a way.
There is REALLY no difference, but there IS a difference, if that makes any sense. I hope I didn't waste your time with this non-answer answer. We will definitely hit the AK RFC in October, but will do DTD only if time allows.