Hi Lynda, welcome aboard!
I have not done either of those Dolphin Port Adventures in Nassau yet, but my daughter and I are signed up for the
Blue Lagoon Dolphin Swim this fall. I have heard rave reviews about both from previous cruisers with Disney and have decided that the Blue Lagoon offers a few better options for us.
My daughter is seven, so she would not be old enough for the dolphin swim at Atlantis, only the dolphin encounter. However, she is old enough for the full swim with the dolphins at Blue Lagoon. If we're going to get in with the dolphins, we'd like the full experience! From other cruisers I've spoken with, it seems that they've experienced more interaction time in the water with the dolphins at Blue Lagoon as well. That is why we've chosen this one over the Atlantis adventure. In addition, we're looking forward to spending a few hours exploring the beach at Blue Lagoon after our adventure with the dolphins is over.
That being said, if you've never been to Atlantis before, you might consider the dolphin swim or encounter there, just to be able to enjoy some time to explore that amazing resort after your swim.
I hope that gives you some more insight into the two different adventures, Lynda! Let me know if I can help with anything else as you continue to plan your magical cruise!