The Grand Floridian is really unique and spectacular....if you are really looking for something special and don't mind the added cost (GF is of course much more expensive than the Swan) then I would recommend the GF. I've stayed there several times and it is my favorite deluxe resort at WDW (we've tried six of the deluxe hotels). I have stayed at the Swan and would highly recommend it, but it is a fun, over the top (meaning brightly decorated) elegant hotel that is similar to many deluxe hotels in Florida. The Grand Floridian is truly unique--it is a turn of the century luxury hotel that is a step up from the Swan and Dolphin and has a very special, magical feeling about it. I think the GF would be a more popular location for weddings and there are plenty of romantic views around GF, including that of Cinderella's castle at night above the lagoon.
You might want to think about if you want multiple buildings (GF has a main lobby w/ restaurants, shops and then separate buildings for most of the rooms) or a hotel w/ all the rooms in one building (Swan). The beds at the Swan and Gf are similar--the Swan has the Westin heavenly beds which are very comfortable but the GF has extremely comfortable beds as well--about the same level. The rooms at the GF are much larger and decorated with Alice in Wonderland wallpaper, with wicker bathroom furniture and Alice in Wonderland bath supplies. The rest of the rooms look elegant and Victorian. The Swan is much more modern and the rooms are more typical, though they are deluxe. Both resorts offer comfortable robes and all the other amenities associated w/ deluxe hotels, like great pool areas (well, GFs is better b/c there are two pools, one which has a waterfall and faces the seven seas lagoon, and has a white sand beach w/ a swing), beach, water activities (Swan has paddle boats while GF has extensive water rentals available--boats, mouses, cruises, etc.), lots of restaurants, good access to theme parks (GF is near MK, Swan near MGM and Epcot), good transportation options around WDW....I would consider the GF more romantic, as there is a band playing in the lobby (which is more elaborate at GF than the Swan, though the Dolphin's lobby is pretty elaborate), and the Victorian theming is more romantic than the Swan's whimsical contemporary theme. There are lots of honeymoon items in GFs shops which makes me guess there are plenty of honeymoons and weddings there.
Both are great hotels, but if cost isn't a factor, GF is by far the more exceptional resort.
Have a great trip
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