You're going to get 6 of one answer, half a dozen of the other!!! I've stayed at both numerous times. If my preferred choice wasn't available, I'd definitely stay at the other.
Decor is the same at both resorts, so take that out of the equation. Refurb is complete on both.
Swan overall is smaller & more intimate, and has queen beds & an extra sink outside the bathroom. The Dolphin is larger, has more hustle & bustle going on (it seems) only has double beds,and only one bathroom sink inside the bathroom. (This being for standarm rooms, deluxe rooms & suites may be configured differently.)
We prefer the Dolphin when the kids are along because the only CS between both is at Dolphin (Picabu), the only laundry room is at Dolphin (none at Swan), the arcade (again none at Swan) and it's closer to The Grotto Pool.
So there you go, your 1st 2 replies were complete opposite opinions (which is why there is an open forum - so you can hear all sides!)