I love giving free advice...
I haven't stayed at the Dolphin so I'll skip right past it...
The WL and AKL are very similar in terms of their standard rooms. The size, layout, beds, etc are virtually identical. Both have modest sized rooms (by deluxe standards) and are quiet, comfortable and have what you need (or just ask for it !).
They are both wonderfully themed and beautiful. The CMs at either one are great - friendly, attentive and helpful.
The WL is very convenient to the MK, AKL is very convenient to AK. The other parks are basically the same time/distance away for either of them and you will have to take buses to get to them (EPCOT, Studios, DTD). AK is closer to the waterparks.
My personal opinion is that the 'fast food' place (The Mara) at the AKL is just a touch better than the one at WL (Roaring Forks), but there are dissenting opinions. I don't think anyone disagrees that 'The Boma' at the AKL is way ahead of Whispering Canyons at WL (the 'mid-priced' restaurants). My personal opinion is that 'The Boma' is one of the 5 best restaurants I've EVER eaten at, period (and that covers territory from Paris to Tokyo). The two 'high-end' restaurants are both excellent.
At the AKL you will be able view fantastic animals from lots of locations around the resort and talk to a lot of folks from Africa that really have kewl stories to tell, but there is the possiblity that your 'standard' rooms will have a yucky view. Many people, myself included, have been upgraded to Savannah view, but it obviously isn't a sure thing. Some of the standard view rooms are OK, some look out toward US192, etc.
The good news is that either place is really great, if I where going in December I would stay at the WL, if I were going in August I would stay at the AKL.