We ate at both in January, and I'd give B&C the edge, but both were great. Just the kids and I ate at B&C--their cheeseburgers were great and the Brownie al la Mode was to die for!
At the Dolphin Fountain all 4 of us had dinner--burger, BLT and chicken strips. The chicken strips were served in cardboard cars, which the kids loved! Very good, but I think the burgers from B&C were better. We didn't get ice cream.
I would say that each had about the same amount of seating area, although there were very few people at the Dolphin.
Either way you can't go wrong!