I've never stayed at Port Orleans, but I have stayed at Caribbean Beach which is also a moderate resort. To me, it's about how much you value the following:
Park Access:
Dolphin > Moderate - Walking to EPCOT and DHS is HUGE for me, and on real hot days, the boat runs more frequently and is less crowded than buses.
Location:
Dolphin > Moderate - Proximity to Fantasia Gardens and the Boardwalk area is also a big deal for me.
Transportation to/from airport:
Moderate > Dolphin - Magical Express is awesome, nothing else needs to be said. You can find shuttles that are between 120 and 150 round trip, but the free Disney service is great. Plus it's got the silly videos and presentation that get you excited for your trip.
Cost:
This depends on when you're going, but I see it as a wash. Without discounts or anything, Moderate resorts in September are just under $200 a night, while the Dolphin would be maybe a little over $200 a night after room fees and such.
Amenities:
Dolphin > Moderate - The rooms are bigger and better, and as someone else said, you can potentially have some really beautiful views. I stayed there 2 nights back in 2010 and had a beautiful view of the Swan and the Tower of Terror.
For me, the Dolphin wins out, even if I have to pay for airport transportation. The free dining has never been available when I've gone, so I can't speak to that, but yes, free dining is another major cost you wouldn't have to worry about. It's really up to what's important to you. For me, the location alone is enough to choose the Dolphin.