As its a resort, people don't usually choose to go to one or the other unless visiting for 1 day (when the obvious choice no matter at California, Florida or Paris is the castle park). It's more why should I visit this park on a second day, and that would be ToT, Crush's, Ratatouille, Avengers Campus, pretty much all of the park's shows (Alice and Stitch are the two non must-dos) and soon Frozen and Lion King. As a whole the park has a pot of good offerings, they're just not surrounded by the exploratory settings of the main park
Weird. I was going to post that the links weren’t working (they aren’t if you click on them), but the pics have appeared in my reply.
I'm not sure why, but since about the end of last decade Art Nouveau is the go-to home style for Disney. Replacing the American Victorian style that previously dominated Disney resorts. Both styles are fairly contemporaneous, so that's not it.
I think there might be a preference to dissociate Disney Adventure World from WDSP and its poor reputation.
I personally consider Art Nouveau very time-specific, and very limited in applicability. There's only so much you can do with it. Hence why it ended, and why it somewhat slipped into obscurity. It's popularity has been on rise for decades now though, to the point of near universal admiration. Many would now even name it their favourite historical style. Perhaps part of the explanation for the AN adoptation by Disney is simply the difference in appreciation of AN between 1970 and 2020. And a decline in nostalgia for US turn of the century styles.