This is a great question. We have stayed in both when not staying at DVC resorts.
My wife and I are completely split:
WIFE: I just asked her and she said, "Dolphin for location, POR for the feel." In other words, she says that POR has a more Disney feel to it, which I agree with. Her first answer was that she would take POR (where we had our honeymoon), but when I reminded her that we went with the Dolphin for a recent trip and that we loved the location (near 2 parks), she said "I guess you are right. I'd go with the Dolphin."
ME: I will be the first to say that POR is a GREAT resort. I consider it to be a deluxe resort at moderate prices. You can't beat the general vibe when walking around the grounds. With that said, I just can't pass up the location for the Dolphin. We love that area. On top of that, the rooms are bigger and nicer, the counter service is open 24 hours a day and the pool area has a more "luxury" feel to it.
Yes, the Dolphin doesn't feel as "Disney" as POR when you are walking around the hotel and grounds. However, the LOCATION feels more Disney, as you look out and see several other Disney resorts, and you can walk to 2 parks.
So..............While you can't go wrong, I would go with the Dolphin.