DH and I do not have kids. We have been to AKL three times and to YC twice. I love them both very much, but they offer different experiences!
AKL: DH and I are animal lovers and a savannah view room at AKL is such a wonderful experience. There's nothing quite like being out on your balcony watching the zebras grazing or the giraffes sauntering in to the feeding area. You will feel like you are in Africa! We love the decor and the atmosphere at AKL. There's really no other place like it anywhere, (well, maybe if you actually went to Africa -- I've never been there so I can't say.) The restaurants are wonderful, too. We love Boma and Jiko -- for unadventurous eaters they do offer plenty of familiar food, but for those of us who like to try something new and different there are lots of unusual dishes to try. We're vegetarians and these two restaurants are among the best vegetarian dining options on property. They also make a good mai tai at the pool bar.
YC: We love the location of the YC right in the middle of the Boardwalk area and within walking distance to Epcot and MGM. We really enjoy walking and I get such a kick out of the fact that we can walk to Epcot from the YC! We also enjoy strolling around the lake at the end of the evening and then coming back to our (lake view) room and looking out across the lake at the lights of the Boardwalk. There are lots of dining choices when you stay at YC: There are good restaurants at YC, BC, the Boardwalk and the Swan and Dolphin and of course the World Showcase restaurants in Epcot are an easy walk from YC and MGM isn't that far away. The atmosphere in the lobby of YC is quieter than that of it's neighbor (BC), but given we don't have kids and aren't really used to all the noise and chaos, we appreciated how quiet it was when we got back to YC at the end of a busy day in the parks.
I guess if I wanted a more relaxed stay, I'd choose AKL because when we go there, we enjoy just hanging out at the resort -- love the animals, the pool, the food, sitting around the fire, etc. If I wanted a more active stay, I'd choose YC because there are more things to do right outside your front door: the Boardwalk, Epcot, MGM, surrey bikes, etc.
As to which is more romantic, that is an interesting question. I find AKL romantic -- the dim lighting in the lobby area, the unusual atmosphere, feeling like you and your DH are thousands of miles away in Africa rather than Florida, dining at Jiko, yes, I find it very romantic. The atmosphere at YC isn't as unusual as AKL, but walking around the lake in the evening and coming back to the room to sit on the balcony with a glass of wine, looking across the lake at the lights of the Boardwalk feels relaxing and wonderful.
